An Electric Airplane That Makes Sense

Hybrid is the word we use now to define a vehicle that combines different propulsion technologies. But we wouldn’t think of calling the most successful hybrid of all time a hybrid. We call it the Diesel engine, or more formally the diesel-electric locomotive.

It was clear more than a century ago that the internal combustion engine had many advantages over steam power. But in a railroad locomotive it was very difficult to transfer the output of a piston engine to the drive wheels. The necessary gears, transmissions, clutches and other hardware just didn’t hold up. And the piston engine had to spin at comparatively high rpm to produce the necessary torque so that made it very difficult to get the heavy train moving.

The solution was to connect the piston engine to a generator. The piston engine turns the generator without gears and clutches and can operate at a constant and efficient rpm. The generator produces electricity that is wired to drive motors on the locomotive axles. Electric motors can generate gobs of torque from zero rpm making them perfect for getting a train rolling and then operating over a range of speeds.

Nobody would think of replacing the Diesel engine in a train locomotive with a battery. But that’s what most people are thinking when it comes to electrically powered airplanes. Just as in a locomotive, an electric motor has many advantages in powering an airplane. But batteries just don’t cut it as an energy source. And I don’t believe battery technology will advance far enough in my lifetime to power an airplane with speed, payload and range similar to our current piston fleet. And who wants to go backward on those qualities?

But if we install an electrical power generating source in the airplane we are freed from the low energy density of a battery but can still gain the advantages of electric motor propulsion.

Electric motors are much more compact than a piston engine of similar output so a nacelle could be designed for low drag, not simply to accommodate the engine.

Electric motors produce torque at low rpm and propeller efficiency benefits greatly from low rpm, particularly when operating at high airspeeds.

A battery could also be used to supply a brief burst of power for takeoff so the actual generating engine would need be sized for cruise, not takeoff and initial climb or go-around. The battery would act like the water injection systems that upped the power in some pistons and turbojets years ago. A couple minutes worth of extra energy would be enough.

With hybrid power the weight and mass of the propulsion system could be distributed ideally within the airframe. Many have tried to locate piston engines midship but the compromise of drive shafts has not worked out well. Even turbine engine efficiency suffers when long ducts are used to feed induction air.

With hybrid power the power producing engine could be positioned in the best spot for weight and balance, and to minimize drag of the necessary structure around it.

Tesla has made lots of headlines with its all-electric battery fueled car. But Porsche has blown Tesla into the weeds with its new 918 Spyder that is a true hybrid with both battery and gasoline engine power. The electric motors that drive the 918 wheels are extremely efficient and powerful and the car has beat all of Porsche’s conventional cars in lap time around the famous Nurburgring track in Germany. The piston engine in the 918 is connected to the wheels along with electric motors, but it seems certain a Porsche with electric motor propulsion only can’t be far in the future.

I think battery-only power is going to be restricted to vehicles–including airplanes–with very limited applications. But a true hybrid holds great promise. The power generating source can be a gasoline or diesel piston engine, a turbine, or perhaps a hydrogen fuel cell, or even some technology not yet invented.

An electric airplane could be great, as long as it’s making its own electrical power. I don’t want to watch my range go out the window just because I turned the heater up or the air conditioning down. However, if you’re goal is to avoid burning fossil fuel entirely and you are willing to sacrifice speed, range and payload there is already an airplane that suits that mission–a glider.

Posted in Mac Clellan's Left Seat Blog | 10 Comments

AARP and the FAA

I’m now a card-carrying member of AARP. Well, I don’t think I actually carry the card around, but it’s at home somewhere. But AARP knows where to find me and I believe every other oldster and they keep our mailbox–both paper and electronic–full.

A headline on a recent AARP “Bulletin” caught my eye. It read “10 Medical Tests to Avoid.” Since I have devoted my life to avoiding as many medical tests as possible I read the story to see how the large panel of medical experts list of unnecessary and potentially harmful tests agreed with mine.

The very first medical test on the list to avoid is a nuclear stress test or other imaging tests, after heart procedures.

The second test on the list was yearly electrocardiogram or exercise stress test in the absence of any symptom or heart disease risk.

What jumped off the page at me is that those are two tests the FAA requires for pilots to get a medical certificate. Any pilot who has had a heart event or procedure such as a stent or bypass or valve replacement will be required to take these tests. Even reporting chest pain will be enough for the FAA to require the tests. And usually the FAA requires the tests to be repeated for each subsequent special issuance of a medical.

The reason the panel of experts recommends against these tests in the absence of symptoms is that they rarely result in any change in treatment. But the tests are invasive and they can yield false positive results that will cause the patient to have unnecessary treatment. In other words, the tests are adding risk with almost no reward.

According to the immediate past president of the American College of Cardiology the nuclear stress and other imaging tests can lead to unnecessary invasive procedures and excess radiation exposure without helping the patient improve. He told AARP readers that focusing on overall health issues such as weight control, not smoking and increasing exercise yield far more positive results than the tests.

But, still, the FAA will require pilots who have had a heart procedure to undergo these tests even though experts in cardiology recommend against them.

The FAA demands that any pilot over 40 undergo a yearly electrocardiogram to get a first class medical no matter what your overall health may be, or the fact that you have no symptoms or history of heart problems. The AARP reports that people between the ages of 40 and 60–which is the core group of pilots who get first class medicals– who have an EKG but have no known heart disease risks are 10 times more likely to get a false positive of a heart problem than for the test to actually find a true problem. This could lead to unnecessary heart catheterization and stents. A healthy pilot could be thrown into the heart disease treatment cycle and testing by a required test that has a high false positive rate.

The FAA is anxious to point out that nearly every pilot can–after undergoing its required tests–be issued a medical certificate with special conditions. And that’s true. But the tests the FAA requires for the initial special medical, and then the repeated tests it demands usually annually, are out of step with the mainstream of medical experts who are actually treating patients and helping them to live healthy lives longer.

AARP is hardly a fringe group and it has a long history of supporting all manner of advanced medical care for seniors. But it is also a sophisticated operation and AARP is willing and able to adjust its medical advice as new research develops.

The FAA isn’t in that group that includes AARP. The FAA is stuck clinging to outdated medical testing requirements and focusing on issues that now appear not to be critical and may be even harmful to a pilot’s health and performance. We tell ourselves that aviation is advanced technology, and in some ways it is, but the reality is change comes slowly for those of us who fly.

Since the majority of pilots are now AARP eligible I hope the FAA takes notice and applies the best medical practices instead of clinging to the way we’ve always done it attitude.

Posted in Mac Clellan's Left Seat Blog | 20 Comments

Nexrad, Rain and Flying

I think it’s wonderful that the internet and satellites and smart phones have given everybody the ability to see Nexrad radar pictures almost anytime and anywhere.

Stancie and her golf buddies study the Nexrad returns as closely as I do before a flight. Sailors, joggers, farmers and almost everybody else stays up to date on the precip shown on Nexrad. But do we understand what we are looking at? Especially when it comes to flying weather?

When we see those colorful Nexrad returns we are probably looking at some form of precipitation. But we can’t be sure the precip is reaching the ground, is obscuring visibility, is caused by a thunderstorm, or know if turbulence is lurking in the radar echo.

That was the challenge for a trip back home from Sun n Fun last week. The Nexrad mosaic picture showed hundreds of miles of radar returns over a broad swath of the middle of the country.  The area was at least a couple hundred miles north and south, but about a thousand miles east to west. Going around in a piston airplane wasn’t an option.

The precip was associated with a slow moving cold front that had become nearly stationary. Thunderstorms–clearly indicated by lightning returns overlaid on the radar image–were moving northeast at 35 to 45 knots along the southern edge of the weather.

But what about that 150 miles or so of solid yellow Level Two return on my satellite weather that was behind the thunderstorms? Was it turbulent? If I found a gap in the storms could I fly on home to Michigan through all of that “yellow” radar return?

My conclusion was yes, the huge swath of yellow radar returns would be wet, maybe bumpy, but flyable if I got past the leading edge storms. The reason I believed that is because there was no gradient. The area, at least 100 miles wide, was solid yellow. The returns didn’t change from yellow to green, or yellow to red, just solid yellow. It was the biggest area of one level of radar return I can remember seeing.

With great cooperation and advice from ATC, and using both the satellite  weather and onboard weather radar to confirm, Stancie and I found a gap in the line of thunderstorms between Cincinnati and Columbus. We watched a cell on the radar pass off the left wingtip, and just to prove it meant business, the storm pumped out quite a cloud to ground lightning show.

Past that cell we turned northwest toward Lake Michigan. All radars showed moderate to heavy rain, but the radar returns didn’t vary from solid yellow. I felt a little like I was flying a submarine as for nearly an hour the rain beat on the airframe, found leaks around the door, and created some P-static on the radios. But the ride was smooth, we were mostly between layers at 4,000 feet and by the time I neared home and Muskegon Airport conditions had improved enough to fly a visual approach.

When I climbed out of the airplane water was pouring out of the many scuppers under belly and tailcone. And I’m sure a little more paint had been knocked off. But we had a good trip, the Nexrad didn’t lie, and it’s something that would have been a real worry before Nexrad in the cockpit. When everything on radar is green or yellow in very large areas with no red or many changes from green to yellow you can’t be assured good visibility and decent ceilings, but you can be sure the wings aren’t going to break off.

Posted in Mac Clellan's Left Seat Blog | 6 Comments

What Will the New Third Class Medical Rules Be?

The FAA announced that it has begun the rule making process to change the requirements for a Third Class medical certificate for private flying. No details have been announced, but the FAA said it is still considering the EAA/AOPA petition to allow a driver’s license to replace the Third Class for private flying in basic airplanes.

Why is the FAA finally responding after years, and even decades, of requests and petitions to change the medical requirements? My guess, and the obvious one, is that Congress has introduced legislation to force the FAA to defend and justify the current medical standards in terms of safety or change them.

The General Aviation Pilot Protection Act that has been introduced in both the House and Senate would require the FAA to expand the driver’s license medical option to a large variety of piston airplanes if it is enacted.  The FAA doesn’t want Congress making any more rules so I think the FAA is now going to finally try to take the lead on an issue that has gained huge momentum.

So what limitations do I think we can expect to be in a new driver’s license medical standard?

First, there will be a weight limit. The reason is that a private pilot can fly any size of airplane. So long as he is not being compensated a private pilot can legally fly an Airbus A380, or Boeing 747. Obviously, the FAA, and probably not even the public or Congress are going to give that unlimited privilege to a pilot without a medical certificate.

My guess is that the new rule will set the upper weight limit at 6,000 pounds. That is the weight in the legislation and it is also a long standing certification break point. Airplanes that weigh more than 6,000 pounds are still in the “small” airplane category of Part 23 but move into a class or category II with more stringent performance requirements.

It’s no more challenging to fly a Cessna 421 than an Aztec but the 421 weighs more than 6,000 pounds and is in the higher certification category. The 6,000 pound break point has been around for many, many years. Since the new rule will need a weight limit of some type I expect the FAA to default to the traditional 6,000 pound threshold.

The safety issue in aircraft weight is the threat to the public. A larger, heavier airplane can simply do more damage and potentially injure more people on the ground in a crash. The FAA will be able to defend some weight limit, and I really don’t think it will be 12,500 pounds where an airplane transitions from “small” to “large” under certification and pilot qualification rules.

I don’t expect any restriction on fixed versus retractable gear. There is no way an airplane crashing with folded wheels is a greater threat to the public than a fixed gear.

I also don’t expect the new rule to exclude twins. Same thing. It’s weight, fuel onboard and other factors that raise the risk for people on the ground, not the engine count.

IFR or VFR? I don’t think the FAA can defend a rule that makes flying IFR riskier than VFR for qualified pilots. In fact, for years many inside and outside the FAA have said IFR is safer because the trained and qualified pilot can control the airplane in the clouds or low visibility.

Will there be a limit on the number of people onboard for pilots flying with a driver’s license medical? I expect it. When a new rule is introduced changing long standing policies the FAA can make a case to Congress that the small but unknown new risk should be limited. If there are fewer people onboard fewer lives are at risk.

My hope is that we will see a limitation of six people total onboard, including the pilot. My guess is that the rule will propose a limit of four. My fear is that the limit will be two.

The bill in Congress proposes an altitude limit of 14,000 feet for the driver’s license medical. I expect the FAA to successfully defend this restriction because it is a fact that nearly all of us lose tolerance for higher altitudes and lower oxygen levels as we age. It would be hard to argue that we drive cars above 14,000 feet so I expect the FAA to hold firm on that altitude.

I am also concerned that pressurized airplanes won’t be eligible for the driver’s license medical for the same reasons as the 14,000 foot altitude limit. If the cabin were to lose pressure at high altitude the risk would be the same or greater as flying an unpressurized airplane above 14,000.

There is a 250 knot airspeed limit in the bill in Congress. It doesn’t specify if that is indicated or true airspeed, but I’m assuming that it is indicated airspeed. There has been a 250 knot speed limit below 10,000 feet for decades so a 250 knot limit on an airplane with an operating ceiling restricted to 14,000 feet wouldn’t be much of a factor.

I hope that I’m wrong and that a new rule that emerges will allow us to fly for our own personal reasons in even broader categories of airplanes. But I hoped to be watching Michigan State play in the Final Four this weekend, too. State was in the game, had a good run and came close. Now we are finally in the game for Third Class medical changes and I expect we will get much, but not everything, that we want, and we think make sense. You must walk before running, and if my hopes come true a new medical standard will at least be a trot and on our way to a full gallop.


Posted in Mac Clellan's Left Seat Blog | 46 Comments

Could Your Airplane Be A PNC

An Aviation Rule Making Committee (ARC) issued a 346 page report to the FAA on how to streamline small airplane certification in ways that maintain and improve safety while cutting costs. In that report is the recommendation for a new certification category called Primary Non-Commercial (PNC).

An airplane in the PNC category could be maintained by its owner, and would not need to use FAA certified equipment or replacement parts. A PNC would be very much like a homebuilt in terms of maintenance and equipment requirements.

To qualify for PNC category an airplane or glider would need to have a standard production category airworthiness certificate, be at least 20 years old, not be turbine powered and be unpressurized. The airplane would need to have a current annual inspection with all ADs addressed. The airplane owner would apply for PNC which would be granted jointly to him and the airplane. The only physical changes required would be placards to announce to passengers that the airplane in in the PNC category.

Once the owner completes a yet to be created FAA approved maintenance course he could maintain his PNC airplane, add new equipment, and modify it. The only requirement is that the owner use aviation appropriate equipment and maintenance techniques and keep very complete records of all modifications and maintenance procedures.

Once each year the PNC would be required to have a condition inspection by a licensed A&P mechanic. This is different from the annual inspection required for standard category airplanes. An annual is intended to confirm that the airplane conforms in every respect to its type certificate. The condition inspection confirms only that the airplane is airworthy.

A PNC could be returned to standard category by going through an annual inspection to determine that every part of the airplane conforms to its type certificate, STCs and ADs. In other words, any non-certified equipment or modifications made to a PNC would need to be removed or brought into conformity for the airplane to return to standard category.

The PNC would actually operate in a dual certification category. The operating limitations of its standard certificate would still apply, but maintenance and modification procedures would not. A PNC could not be used for hire in any way, except the owner could pay a flight instructor to fly with him in the PNC.

The owner of a PNC could also make major modifications but that would put the airplane into a Phase 1 flight test program similar to newly built or highly modified homebuilts. For example, if a PNC owner dropped a 300 hp engine into his Skyhawk that would almost certainly require a Phase 1 flight test program. But if an owner installs non-certified avionics, for example, no additional approval would be required. Or he could install an improved restraint system, or better wheels and brakes and so on without needing approval. Many of the better and less costly equipment options that are now available for the homebuilt airplane could be installed in the PNC.

The ARC report on changing FAR 23 is 346 pages long, but there are still missing details of how the changes would exactly work. In one part of the report it recommends the PNC be limited to any fixed wing CAR 3/FAR 23 airplane that is not turbine powered or pressurized. In another section you can see a proposal that limits PNC to basic fixed gear singles with no more than four seats. Who can guess what a final rule may be.

In many respects I think PNC airplane owners will self-sort to basic airplanes, including classics and antiques. It makes sense to do your own maintenance on a basic airplane where construction methods and materials are common and systems are simple. To do your own maintenance on a high performance rectractable, for example, is more daunting, would demand more specific tools, and may risk your investment.

For example, a 20 year old A36 Bonanza is still worth a lot of money. If an owner converted the Bonanza to PNC, made many non-certified changes, and then wants to sell it what will it be worth? Less than a standard A36 I would guess because a new owner may not agree with the changes the PNC owner made. The ARC is very upfront about the airplane value issue and they believe that risk of resale value will restrain really big modifications to many airplanes.

So what are the chances we will see the PNC category become a rule. It’s hard to say. Even though the PNC was in the final ARC report it did not make it to a final version that Congress requires the FAA to adopt. The fact that the committee recommends it is powerful, but not a done deal.

Most of the recommendations in the report deal with the process of certification, and how a manufacturer can demonstrate conformity with less variability and uncertainty. Those are worthy goals, but not many are concrete actions. Creation of the PNC category is a very specific recommendation, not a process change.

Yes, the devil is still in the many details of a PNC that may emerge from the FAR 23 rewrite. We can keep the pressure on FAA to include the PNC even though it is not yet under the Congressional mandate.

I think the PNC fits in perfectly with the growing demand for changes in the Third Class medical. When flying is totally personal and private it should be lightly regulated. There is no reason that an airplane built in a factory can’t be maintained and updated by a trained owner just as owners of experimental airplanes have done for decades.

Posted in Mac Clellan's Left Seat Blog | 95 Comments

Aspen and Bendix/King Bend the Value Curve

Aspen 1000 VFR PFD

To me value means getting more for the same or less money. With two new products from Aspen and Bendix/King we actually have capabilities that just weren’t available for most personal airplanes before. And the price is what makes them a great value.

For airplane owners who fly VFR only–which is by far the majority–you can now get an Aspen flat glass PFD priced for the way you fly. And Bendix/King has introduced the AeroWave 100 satellite communications transceiver that will keep you wired to the internet and email world in flight.

The Aspen 1000 VFR flat glass PFD is the same size as the company’s other systems so that it fits into the space occupied by the attitude and directional gyros in the panel.

The VFR display uses the same non-spinning electronic gyros to show attitude and slaved heading, along with an electronic air data computer to calculate airspeed and altitude. The system also has Aspen’s internal backup battery that will keep it functioning for at least 30 minutes if ship’s power is lost. With the Aspen you can toss the vacuum pump and still have precise and reliable attitude and heading.

The difference is the VFR unit doesn’t have exactly the same software as the 1000 Pro series so it shows a compass card instead of an HSI, and there aren’t glideslope pointers and some other details IFR pilots need. But the VFR unit costs only $4,995, around half of the IFR system.

The great news is that the Aspen VFR system has the same hardware as the IFR unit so it can be upgraded to IFR capability at anytime by purchasing the IFR qualified software. You can also add Aspen’s synthetic vision to see the terrain ahead and under you. And most all of Aspen’s other options are also available.

What Aspen did is keep all of the TSO qualification and other requirements so the VFR system can be installed in a standard category airplane without charging you for capability you are not likely to want flying VFR. Installing the Aspen unit will be as inexpensive as possible because it fits with essentially no instrument panel modifications.

Satcom systems have been flying in large business jets for several years, but the Bendix/King AeroWave system is sized and priced for just about any size airplane, including piston singles.

The complete AeroWave system weighs less than 15 pounds, and the antenna is only about twice the size of a standard GPS antenna. But the real magic of the AeroWave is the price of $19,999. Any other satcom system I’m familiar with costs more than $100,000 and is too big to fit on typical personal airplanes.

Part of the AeroWave advance is Bendix/King technology, but equally important are new more efficient satellites. Earlier satcom systems require very high gain antennas to communicate with the satellites. Often the antenna needs to be steered to point at the satellite as the airplane moves.

The AeroWave can use a low gain antenna with no moving parts and still deliver high speed data reception so you and your passengers remain in our normal “wired” world for the entire flight.

Bendix/King has not yet announced which satellite network AeroWave will use but did say the fee will be by the hour of connectivity, not by the amount of data received as many other systems do. The company says the data fees will be a fraction of existing satcom systems and, because the fee is based on time not amount of data, the cost will be predictable.

The AeroWave can be connected to a wireless router so all your personal electronic devices work in the airplane. Staying connected will be a huge advantage for passengers, and satcom could also be a critical safety link for pilots in an emergency.

Both the Aspen VFR flat glass and the Bendix/King AeroWave give us new and more capability in our airplanes for a whole lot less money. That’s value.

Posted in Mac Clellan's Left Seat Blog | 46 Comments

Annual Anxiety

Every airplane owner knows the feeling. You take your airplane to the shop once each year for the inspector to go over it with a fine tooth comb and find everything that is wrong, and try to guess what may go wrong with it in the future.

When your airplane heads in for the annual there is no way to know with certainty how long it will be down, and what the final bill will be. And we are talking potential disaster here. If a significant internal failure is discovered in an engine and it must be overhauled or replaced many airplane owners are staring at a $50,000 bill.

My experience over decades of airplane ownership is that when you have no squawks at annual time, look out. Just when the airplane and all of its systems seem to be working perfectly, the inspector will find some major problems you had no idea existed.

That was my situation for this year’s annual. The airplane was running great. The only maintenance issue I was aware of was a leaking nose gear strut.

A few years earlier I had the shop add Granville Strut Seal to the nose oleo and that bought time sealing the leak to very minor fluid seepage. Granville works to soften and swell the O-rings in the struts to hold the hydraulic oil and nitrogen in. The stuff is widely used in all types of aircraft and it works. If you have a seeping oleo strut ask your shop to add the Granville kit. It’s available from most suppliers like Aircraft Spruce.

But now the fluid leak was back to the point where the nose strut had to be serviced about every six months. The only practical way to disassemble the nose gear strut on a Beech is to remove the whole gear leg. The overhaul parts—O-rings—cost only a few bucks, but labor is going to be several hours for an experienced shop so you’re looking at a $500 tab at best.

The only other actual evidence of a maintenance problem I discovered on the day I opened the hangar door to fly to the shop. There was a fuel stain on the left main landing gear and tire. That hadn’t been there before. The fuel lines run through the wheel well so I hoped it was just a loose fitting. But the two-speed electric fuel pump is also in the well over the main gear. That pump is very expensive to overhaul or replace.

In short order the shop called to confirm my fear. The electric fuel pump was leaking. But, the shop also found a certified repair station that could overhaul the pump for one third the price of an exchange saving more than a thousand bucks. Great.

But in the same call I learned two cylinders were leaking too much around the piston rings to pass inspection. Not exactly a surprise as they had over 2,000 hours on them. Since my flying activity is not what it used to be I’d like to get a couple more years out of that engine so I told the shop to replace them with overhauled cylinders. The engine was running fine, oil consumption was stable and well within limits so nothing bad was going to happen suddenly, but the cylinders were worn beyond limits.

The other “surprises” were some small oil leaks around an alternator gasket and cam cover and seeping case spine bolts and that sort of thing. The inspector also found that my whiskey compass was out of whiskey. I guess I never look at the thing so I hadn’t noticed. Compass fluid has such a distinct smell that you usually smell a leak before it’s visible. But not this time.

There was also a problem with the lower rudder bearing. When the inspector moved the rudder he heard a loud clunk. I had moved the rudder on preflight and heard nothing. But when the fairings were off they could see the bearing had corroded and needed replacement.

As has been the pattern over the past decade or so the annual bill zoomed past five figures. It’s hard to believe so much went wrong in a year and just under 100 hours of flying. If there had been no annual would safety have been compromised? Not immediately. The fuel pump leak was not good because fuel outside the system is at least a small hazard. More importantly, if the pump failed totally I would have been stuck someplace because it is almost impossible to start the engine without the electric pump to prime it. The other repairs and replacements probably wouldn’t have created safety issues for many hours to come and would almost certainly have issued some obvious warning.

But there was one important discovery the shop made and fixed that was a very real threat to the health and safety of me and my passengers. The boarding step mount was cracked badly. The crack was under the edge of the fuselage where I would have needed to lay on my back to see it during a preflight so not a great chance I would have found it on my own.

If that step had given way while I was climbing up to the wingwalk, or even worse, broken when I was stepping down, the result would have been a fall with at least cuts and scrapes, if not broken bones. So, for $195 an immediate safety risk was found and corrected. As for the other many thousands of  bucks, well, rules are rules, and annual anxiety will continue for all airplane owners.

Posted in Mac Clellan's Left Seat Blog | 18 Comments

When Icing Certification Made Sense

Certifying airplanes for flight in icing conditions is a fairly new regulatory concept, particularly for non-transport category airplanes. I know, everybody calls it FIKI for flight in known ice certification, but the rules, such as they are, call it icing, not known icing.

For decades airplane manufacturers installed ice protection equipment on a variety of airplanes with no certification implication at all. Deice boots were common in the 1930s on multi engine airplanes. Propellers were protected by slinging alcohol on the blade roots, and the same stuff was used to prevent ice formation on windshields.

Electrically heated propellers and windshield hot plates became common many decades ago. And the weeping fluid TKS anti-ice system dates back to WW II when it was used on British bombers. All of the Hawker 125 series jets use TKS starting in the early 1960s. TKS seems new to piston owners, but is nearly as old as boots in the ice wars.

Many thousands of GA twins from Beech, Cessna, Piper and others were equipped with boots and prop ice protection but nobody thought about certifying the airplane to fly in ice. The boots were tested at least some, they worked in terms of inflating on command, and usually broke the ice off.

Think of all of the Beech 18s and Cessna 400 series twins that slogged through all kinds of weather, including icing, working for a living. And they were not certified for icing. Neither was Piper’s Aztec or the initial run of Navajos. Or the Aero Commanders, or even the Learjet 23 or Saberliner.

The idea of certifying an airplane with ice protection for flying in icing made as much sense as certifying a weather radar equipped airplane to fly in thunderstorms. Radar helped you avoid the worst and the boots kept you flying while you escaped the ice. Everybody knew there were thunderstorms that could break the wings off, and that there is icing that can overwhelm any ice protection system.

Certifying for flight in icing really took hold as turbine engines came along. It quickly became obvious that ice building on the inlet to a turbine engine could choke airflow and kill the engine. Equally threatening was ice that built up on the engine inlet and then broke off and was swallowed in chunks that could destroy compressor and turbine blades. Something had to be done.

So standards of liquid water content and droplet size were devised to test engine inlet ice protection. Then the concept of testing and approving ice protection spread to the rest of the airplane. But the “rules” were contained in FAA advisory circulars, not actual certification rules, and the ACs applied only to transport category airplanes which weigh more than 12,500 for takeoff.

I’m not sure why, but in the 1970s Cessna decided to certify some of its piston airplanes for icing. The 337 Skymaster and 210 singles were first up. The only procedures that existed applied only to transport airplanes, not GA piston airplanes, but the FAA somehow adapted those standards to the 337 and 210 and they were certified for icing.

You don’t need much experience in weather flying to know that an ice certified 210 is not going to survive as much ice as a non-certified King Air, or Beech 18, or even Cessna 310. If nothing else the 210 engine would cook because ice buildup on the cowling restricted cooling air flow just at the time you needed every single horsepower to lug the ice the system couldn’t remove.

So now pilots were told it was OK to fly a “certified” piston single into icing. Before that pilots were told to stay out of icing, and if you find it activate the boots and change altitude, or course or do something to escape. Was icing approval a safety advance? I don’t think so.

There are thousands of airplanes—nearly all piston twins—that are equipped with ice protection but are not approved for flight in icing. Nor are they specifically prohibited from flying in icing. A perfect status, I say. If you know ice is there nobody flies into it. If you find icing, you do your best to exit. Who needs to certify that?

But it’s too late. The FIKI horse is out of the barn. Airplanes are being certified to fly in laboratory icing and pilots are given a level of comfort that may not be warranted. And now an AD is being issued to prohibit flight in icing for thousands of Cessna twins that were built and equipped under the old concept of not approved, but not prohibited. Icing should get every pilot’s attention no matter what the certification limitations of the airplane may be and new limitations shouldn’t change that.

I applaud icing tests and the improvements they can lead to. And I’m happy to see effective ice protection on a growing variety of airplanes. But I much prefer the old attitude that ice protection helps you escape, but there are icing conditions out there that can bring down any airplane, particularly any piston powered airplane no matter the certification status.

Posted in Mac Clellan's Left Seat Blog | 11 Comments

F vs. C Temp Fight Is Over for Pilots

Like many of you I grew up flying in a bifurcated world of air temperature. On the ground we used Fahrenheit but as soon as we lifted off air temperature considerations were in Centigrade. Or Celsius some called it.

Actually, I’m not so sure it was that clean cut of a situation when I learned to fly 45 years ago. As I remember the winds and temperature aloft forecasts were reported in degrees C. But I also remember a lot of conversion from C to F going on in ground school and when making flight plans.

The rest of the world had been on the Centigrade scale for hundreds of years. There was a concerted effort in the U.S. to move entirely to the decimal system when I was in school during the 50s and 60s. We were told the decimal system made more sense, was easier to use, and the U.S. couldn’t hold out against the world.

Highway signs began to appear in both statue miles and kilometers. The same for speed limits. Even domestic cars grew a second scale on the speedometer to show kilometers per hour. The transition from the English system of weights and measurements to the international decimal system was a certainty many people believed.

But the change didn’t happen. Even the English have largely converted to the international decimal system, but in the U.S. we haven’t. That says something about the U.S. psyche but I’m not sure what. In any case, that’s beyond our concern as pilots.

Aviation in the U.S. did finally make the transition to the international system for air temperature. We haven’t gone to meters for distance and altitude, or hectopascals for altimeter seeting, but we did change to C for air temperature. I think the reason is that using degrees C for air temp is just so simple and easy in flying that why would anyone continue to resist.

In aviation we care most about two air temperatures—freezing and ISA, the international standard atmosphere. We care about freezing because that’s the temperature were water in the air can become ice. We care about ISA because all airplane performance is measured against that standard.

On the C scale 0 is the temperature where water freezes. Ok, all of you with access to Google can save your emails. I know that the C scale was modified years ago to match with Kelvin and water freezes and ice melts at about .01 degrees C above zero. Since I don’t have a thermometer that good I’m sticking with zero as the temperature for ice.

ISA air temperature at sea level is 15 degrees C. An easy number to remember. Any air temperature above ISA robs engines and airfoils of performance, while temperature below ISA adds to potential power output and lift. We need to know if we are above or below standard when planning any takeoff to know how the airplane will perform.

Another great benefit of using degree C for flying is that the standard lapse rate—the rate at which air cools with altitude–is 2 degrees per thousand feet. On the F scale the lapse rate is 3 point something degrees which is really hard to work in your head compared to working with 2.

The standard lapse rate is essential to know because if the air temperature is above standard at your altitude your airplane loses performance while it gains if the temp is colder. You can always look up ISA for your altitude in the POH, but it’s so easy to multiply your altitude by 2, adjust for the sea level standard of 15, and know ISA for your altitude. For example, at 5,000 feet the standard air has cooled 10 degrees. Subtract 10 from the sea level of 15 and you know ISA is 5 degrees C for 5,000 feet. Look at the air temp gauge and you know if your conditions are above or below ISA.

That calculation works up to 36,000 feet where ISA stops cooling with altitude and remains at -56.5 degrees C. If you are ever able to fly above 75,000 feet the air—what little is left of it—starts to warm up with altitude.

U.S. airplane manufacturers were the first to make the switch to all-C temperatures in performance charts. When we listened to ATIS the airport temperature was still being reported in degrees F until about 15 years ago, but the charts in the book used C for larger airplanes first, and then most GA airplanes by the 1970s and 80s. It was just an easier and more logical system to use.

Finally, in the mid 90s the FAA converted to the METAR international standard for airport weather observation reporting. In the old sequence report observations of ceiling and visibility came first, and surface temperature was listed in degrees F. The METAR moved the wind into first place and changed surface temperature and dew point to degrees C. Gone was the need to convert F to C to use the charts to calculate takeoff performance.

It took some time but I made the total transformation from F to C when flying years ago. The only temperature conversion I now work is after I listen to the ATIS for arrival. I still haven’t made the complete switch to C for my personal comfort so when I hear the ATIS report of airport surface temp in C I glance at the dual scale on the air temp gauge to know if I will be hot, cold or just right when I open the airplane door after landing.


Posted in Mac Clellan's Left Seat Blog | 30 Comments

GPS: It Took A Long Time

Last week Garmin reminded us that it was 20 years ago that the GPS 155 was the first to receive FAA approval for IFR navigation en route, terminal and for approach. Even in the slow moving world of aviation technology 20 years is a long time. But the surprising saga of how GPS got to be what we know today goes back much further.

I’ve been following and writing about GPS for nearly 40 years. I started trying to describe the technology in 1975 when I was working in the communications department at Collins Radio, what we now know as Rockwell Collins. The then large conglomerate, Rockwell, had just acquired Collins and the sometimes bumpy road to integration was under way.

Collins engineers had been working on a previously secret satellite based navigation system for the Air Force called Navstar. Collins had the contract to build the first receivers and another division of Rockwell was building the satellites.

Navstar was first, foremost and at that time exclusively a weapons system. Or more precisely a weapons guidance system. It was the winning technology after years of research, trial and error to find a way to locate and direct military weapons, missiles, aircraft, ships and even individual soldiers anywhere on earth.

The Cold War was burning hot at the time and Navstar would give the U.S. a big edge in precision weapons delivery. Before Navstar inertial guidance was the best technology for directing weapons to their targets over long range, but inertial has many limitations, including accumulating errors as time and distance go by.

I don’t know for sure why the Air Force decided to begin talking about Navstar. Maybe the program became too big to keep secret. Or maybe it understood that once a signal is broadcast it can’t really be a secret. Or maybe it wanted some PR. Whatever the reason by 1975 we could start talking at least a little about Navstar and its fantastic capabilities. Navstar performance was still secret and we could only say accuracy was “within 10s of meters” and there were only a few test satellites overhead. But Buick signed up to be the first auto maker to eventually offer Navstar guidance. And Collins was able to show off the precision of Navstar guidance by flying its Sabreliner under the short and small reception footprint of the few test satellites.

The FAA reaction to Navstar was no, never, will the signals be used for civilian airplane navigation. Don’t even think about it. The Air Force reinforced the FAA by letting everybody know that it is intentionally degrading the accuracy of Navstar by “dithering” the signal and only military receivers with “selective availability” could receive the true nav accuracy. And on top of that the Air Force said it will turn off Navstar at any time it wants and without any warning or notice.

You can imagine how this played in the rest of the world. Even our allies were never ever going to use a nav system controlled by the U.S. military. The FAA and Europeans threw millions at the microwave landing system (MLS) while all the while swearing on a stack of whatever that we civilians would never be allowed to use Navstar guidance in the national airspace system.

But, once you put a signal out there, somebody is going to figure out how to receive it and use it. And people did. Before long people were creating Navstar receivers for all sorts of uses. None of those receivers were approved for anything, but they didn’t need to be, except in aviation for IFR navigation.

Soon the Navstar name was dropped in favor of the more descriptive Global Positioning System. The FAA and Air Force remained adamant that GPS couldn’t be used for any approved navigation. The Air Force kept telling the public it would degrade GPS accuracy and may turn it off at any time it saw a threat. But companies kept building ever more capable navigators and GPS began to work its way into all aspects of our lives.

By the Clinton administration the politicians realized the Air Force attitude was untenable. Taxpayers understood that they had paid for the GPS technology development and for the satellites and wanted to use what they had paid for. President Clinton was the first to order the Air Force to knock off all the GPS denial talk and remove the intentional error from the system.

The FAA did a complete 180 turn and announced plans to convert to a complete satellite based nav system. There would be no more ILS approaches and the VORs would be decommissioned on a schedule that was too rapid to be believable. WAAS solved the problem of insufficient vertical accuracy and signal loss warning time so LPV approaches match the precision of ILS. The FAA remains committed to a satellite based air space system but the timetable has slipped to 2020 and beyond.

And the rest of the world jumped onboard. The Europeans have the Galileo satellite system, the Russians have GLONASS, and China and others are developing their own more or less compatible GPS systems and all will eventually be integrated into worldwide system.

The surprise wasn’t that politics, both military and civilian, got in the way of all of us using GPS. The pleasant, and rare surprise, is that all of us won. Most new technology is launched with promises that can’t be kept. GPS was launched with promises that the world, and particularly civilian pilots, wouldn’t be able to use it. Funny how hard it is to predict where technology will lead.

Posted in Mac Clellan's Left Seat Blog | 11 Comments