Can You Install ADS-B Now? Maybe Not

So you’re ready to take the plunge and install equipment that meets FAR 91.225 and 91.227 requiring ADS-B “out” for flight in regulated airspace after the end of 2019. Can you do that? Is there a certified option available for your airplane? Maybe. But maybe not.

If you built your own airplane, or bought an E-AB that someone else built, the answer is no. If you own an LSA the answer is also almost certainly no. And if you own a pretty new standard production airplane with a factory installed flat glass avionics system the answer is also probably no.

Sounds crazy, doesn’t it? The FAA and the avionics industry are urging all airplane owners to act now and get certified ADS-B equipment installed and approved because there won’t be enough radio shop capacity to handle the crush of installs at the last moment.

But the FAA has tied itself into such regulator knots that many airplane owners simply don’t have a certified path to ADS-B compliance.

When the FAA was finalizing the ADS-B rules more than six years ago it was, and remains, extremely concerned that all approved equipment meet a very high standard for precision and reliability. After all, when we make it to an all-ADS-B world an airplane will be invisible if its system doesn’t function. Worse yet, if an ADS-B broadcasts inaccurate position, altitude, velocity and so on it could create a collision threat rather than resolve it.

So the FAA made the ADS-B certification rules extremely strict. For example, initially every specific piece of equipment must be approved in each type of airplane. There would be no multi-model (AML) STCs granted. That idea lasted for a couple years until it became unworkable so now there are AMLs covering installation of specific ADS-B equipment in hundreds of standard category airplanes. But so far the FAA is clinging to its individual model approval for helicopters.

Under its number one priority to keep ADS-B rules strict the FAA apparently forgot about homebuilts and other experimental airplanes. The rules require an STC (supplemental TYPE certificate) or TC (TYPE certificate). I capitalized type because that’s what is missing in an experimental. By its very existence an experimental aircraft has no type certificate. It’s a one-off, no matter if homebuilt, prototype, exhibition or developmental.

Maybe ADS-B in a homebuilt could be certified by an FAA field approval where an FAA office approves modification of a specific airplane. But that doesn’t seem to work for homebuilts. It is the builder who is the “approved” modifier and equipment installer. A field approval normally is granted to an individual based on work performed on other airplanes of the same type. There’s that word again.

Some builders are installing ADS-B equipment that is potentially certifiable and believe they have met the rule. But they haven’t. The rule requires flight manual supplements, operating restrictions, a performance test and other approved paperwork and there is no way for a builder to get there.

Under the ASTM rules that govern factory built LSA only the manufacturer can approve any change in the airplane, including installation of avionics. So there can be no STC for an LSA because there is no FAA type certificate for the airplane. No radio shop can ask for a field approval because only the manufacturer, not the FAA, can approve any change. How will this be resolved for LSA owners who want and need ADS-B capability? The situation is particularly worrisome for owners of LSA whose manufacture has exited the business. Who will spend the money to get an ASTM approval for those airplanes and how would the process work?

And the airplane left out of a path to ADS-B so far that is most surprising is a newer airplane with glass cockpit. When a complete avionics system is installed by the airframe manufacturer it is usually part of the type certificate, just like the ailerons or wing structure. The only way to add ADS-B capability to such systems is for the manufacturer to amend the TC, which can be cumbersome, and expensive and so far none have complied that I know of.

In some other airplanes a manufacturer delivers a new airplane with a complete integrated avionics system under an STC. But the complication there is that the airframe manufacturer may own the STC, or almost certainly controls the STC. That means that even though the maker of the avionics has ADS-B equipment designed and ready for certification it can’t get approval on its own because it doesn’t control the STC.

I’m sure there are other situations that I’m not thinking of where an airplane owner ready to invest in ADS-B out equipment simply has no path to certification. And changing FAA regulations never happens quickly so I don’t know how these conundrums will be resolved.

If you have a homebuilt or LSA what can you do? The only sensible answer is to wait on the FAA. If you buy and install equipment that you think can be approved in the future you may guess wrong. If you have an airplane delivered from the factory with a fully integrated avionics system you’re stuck waiting, too. So the mixed message from the FAA is the standard hurry up and wait.

Posted in Mac Clellan's Left Seat Blog | 24 Comments

A Year Is Too Short

I’m not exactly sure when or why the year–12 months–became enshrined in so many aviation regulations. But it did. And it’s not nearly long enough, particularly when it comes to annual inspection of our airplanes.

There is no question that calendar time, not just operating time, exacts a toll on any machine. So inspection intervals based on the passage of time make sense. And maybe at some point the passing of a full year was reasonable cause for an inspection. After all, wood left out in the elements can degrade a lot in a year. And so could the cotton fabric that covered the airfames. And the steel tube that was often used for primary structure could rust very quickly.

But those days are long gone. Of course, tube and fabric airplanes still exist and are still being built, but the fabric is synthetic that lasts for decades and corrosion control and wood preservation has vastly improved.  And the big majority of airplanes are made from aluminum, and there is a growing number of composite construction airplanes, all of which age much more slowly than the fleet did when the annual inspection requirement was established.

What we’re left with is the wear and tear of significant disassembly necessary to complete an annual inspection. Simply because 12 months have passed, an airplane that is working just fine has to be torn apart just to be sure it’s working, and that is guaranteed to cause at least some wear, and also create at least a few issues when things are reassembled.

Even worse is that we are all flying fewer and fewer hours. Meaningful annual flight hour averages for typical personal airplanes are impossible to come by, but I’m convinced the annual average of flying is somewhere around 50 hours. The flight times are so low there is simply no way we are wearing our airplanes out from actual use.

The people who do fly a lot–the airlines and business jets–have made great progress in moving beyond arbitrary calendar time limits. The Maintenance Steering Group (MSG) is an industry committee that works with the FAA and manufacturers to design in maintainability. The goal is to increase the time between maintenance events and make line replacement of failed units quick and inexpensive. Many newly designed jets have a basic maintenance interval of 600 flight hours or more. That means you only check the oil and tire pressure and stuff like that for the entire 600 flying hour interval.

We can’t redesign our airplanes to an MSG standard, but as Mike Busch has repeatedly pointed out, we could employ evidence based inspection and maintenance in place of the arbitrary annual. And the evidence is not on the side of an every 12 month disassembly to find critical problems.

When you think about what calendar time does to an airplane versus the wear of flight everything bad that can go wrong when an airplane is not flying happens very slowly. I guess it’s possible a crack could develop in a motionless airplane, but not very likely. Wear of moving parts doesn’t happen without flight. Yes, lubricant does dry out, hoses and rubber seals do decay, but that happens over many years, especially to airplanes stored indoors.

Internal engine corrosion is a threat to an airplane that flies little, but only to your wallet. If a corroded cam lobe rounds out, or a rusty cylinder wall wears, the engine won’t stop suddenly. Oil consumption and rough operation will tell you it’s time for maintenance if corrosion has attacked your engine.

What we need is to focus inspections on flight hours and stretch out the calendar intervals to a point that makes sense. Certainly a full inspection every other year would not compromise safety for an airplane that flies 100 hours or less a year. And that would cut routine maintenance costs by half. And for many of us maintenance is the largest component of airplane ownership cost, so half would be big, and a safe place to start. For example, if the requirement were 200 flying hours or two years between what is now an annual inspection, whichever came first, most of us would save a bundle.

Just as we are all demanding that the FAA overhaul the third class medical because there is no evidence it adds to safety, it’s time to do the same for the annual inspection. A year is just too soon to take a personal airplane apart.

Posted in Mac Clellan's Left Seat Blog | 25 Comments

Want A High Performance Two-Seater? Build It Yourself

The most popular category of homebuilt airplane is a two-seater. And there are even a bunch of single seaters flying. And most of these airplanes offer high performance either in speed or aerobatic capability, or both.

But if you look at standard category two-seat airplanes you find only the most modest performance. Even though Cubs, and Champs, and Cessna 140s/150s and many other types were built in enormous numbers they are also among the slowest and least powerful production airplanes.

It’s hard to think of a high performance one or two-seat standard production airplane because there have been so few. There may be an airplane I’m forgetting, but the Mooney M18 Mite is the only production single-seat airplane that comes to mind. Even the Pitts, when it was put into production, was the larger two-seat version.

The only fast production two-seater that comes to mind is the Wing Derringer, a very small piston twin that was very briefly built in the late 1970s. The Derringer evolved from the Thorp homebuilt. I don’t believe more than a dozen of the tiny twins were manufactured before the company failed.

The reasons high performance single and two-seat airplanes haven’t succeeded in standard category production are complicated, but can be distilled to one overall factor–cost.

The reality in airplane production is that building an airplane a little larger to accommodate four, even six, instead of two people costs comparatively little. The costly components such as engines, landing gear, systems, avionics and so on cost the same for a high performance two-seater or installed in a four-seater. And the demand for at least four seats is simply larger so that tips the scales for an airplane manufacturer.

You can see this phenomenon at work in several production airplane families. The Bonanza line is probably the best example. When Beech introduced the Model 33 Debonair it had lower power and thus less performance than the Bonanza. But as the Model 33 evolved Beech installed the same 285 hp engine as the six-seat Model A36 so performance was about the same. Then Beech dropped the name Debonair and called all of the models Bonanzas.

But it soon became apparent that is cost Beech only a little more to build the six-seat A36 compared to the four-seat F33A Bonanza, but the six-seater commanded a significantly larger price and demand in the market. The F33A went out of production years ago but the A36 continues on.

Cessna and Piper reached similar conclusions with their two-seat lines. Cessna found it no longer economical to build the two-seat 152, but the four-seat Skyhawk is in production. The same thing happened at Piper where the two-seat Tomahawk has been long gone while the four-seat Warrior/Archer is still a success.

In kit airplanes we have seen the opposite trend. High performance two-seat designs dominate while four or six-seat kit airplanes are not that common.

I guess it’s the mythical “invisible hand of the market” at work. Companies that manufacture standard airplanes have to appeal to the largest possible audience. Companies that make kits must appeal to pilots who want something they can’t get anywhere else.

So if you want to fly fast in a very maneuverable airplane there is a solution that manufacturers can’t provide–a kit airplane. And the numbers show more and more pilots don’t want to haul around extra seats just to fly fast and far.

Posted in Mac Clellan's Left Seat Blog | 8 Comments

Do the FARs Still Matter?

I was looking out the window of the diner on the main street in our little Lake Michigan beach town and saw a big white SUV drive out the wrong way from the one-way entrance for the parking lot across the street. There are signs forbidding this, and arrows and words painted on the pavement. There’s no way the driver could have been unaware he was breaking a rule.

There was no conflict with other cars so the rule defiance caused no threat. I can only assume the driver simply believed the rules didn’t apply to him, at least not at that moment.

The incident made me think about an increase in fundamental FAR breaking that I have been seeing in NTSB accident reports over the past few years. I read every fatal accident report when it becomes final. I haven’t tried to tally how many reports find FAR violations, but I am certain the number is growing.

Of course, most serious accidents involve some sort of rule breaking because, in general, it’s against the law to crash. Operational rules infractions have been an accident cause forever. For example, the VFR pilot who flies into weather below VFR minimums obviously chose to break an FAR. So did the pilot who knowingly–or at least should have known–about conditions that were beyond his capability or that of his airplane. That violates rule 91.13, the careless and reckless clause. And so does buzzing and many other inordinately risky things some pilots do in airplanes.

But what I have been noticing is an increase in violation of fundamental FARs, rule breaking that requires not just one wrong decision in the cockpit, but many, even hundreds of decisions to ignore the rule while safely on the ground.

For example, it’s not uncommon now to read in accident reports that the airplane has not had an annual, or in the case of experimentals a condition inspection, for years before the accident. ADs are frequently ignored and increasingly airplane owners have not properly re-registered their airplanes as required.

NTSB reports show that pilots frequently blow off currency requirements for the basics such as making the three landings and takeoffs in the past 90 days before carrying passengers. Often the biennial flight review is years in arrears. It’s not rare to read about pilots who lacked a category or class rating to fly an airplane, or even to have any valid certificate of any level at all.

The most common rules infractions reported by the NTSB involve medical certification. Autopsies of pilots killed in accidents commonly show the pilot had known medical conditions not reported to the AME. And the NTSB finds that a huge number of pilots, maybe even a majority, involved in fatal accidents are taking medications not reported or approved by their AME.

But just like the driver I watched break the one-way traffic rule, pilots breaking non-operational rules are seldom the cause of an accident. For example, the NTSB goes to great length to examine the maintenance records of a crashed airplane, often finds huge rule violations, and then notes that everything in the airplane appears to have been working normally before impact. And that makes sense. Is an airplane going to break just because it’s been 14 months, or two years, or five years since its last annual inspection?

The same goes for rules like pilot currency. Do you forget how to land if you haven’t done it in 100 days instead of 90? Has the biennial flight review prevented an accident? Does even having a pilot certificate prove that you know how to fly?

And the situation is really murky in the medical area. The NTSB will often list several drugs found in a pilot’s system, including alcohol and illicit drugs, and then note that there isn’t direct evidence the drugs contributed to the accident. A total pilot incapacitation in flight is quite rare, and more often than not, the pilot who becomes incapacitated was not breaking any rules.

Private flying is very much a self-regulated activity. In more than 45 years of flying nobody has ever asked to see any paperwork on me or my airplane except when I voluntarily go for training, a new rating, or take my airplane to the shop for maintenance. Unless you are involved in an accident or serious incident you can almost certainly fly on ignoring nearly all of the FARs without much fear of being caught.

But historically we haven’t done that. The pilots I know and grew up with wouldn’t think of flying their airplane to the shop for an annual without a ferry permit even if it was only one day beyond the limit. And we all pay attention to the 90 day currency rule, even though it, like nearly all rules, is totally arbitrary. And on and on.

Is that attitude changing? The findings in NTSB accident reports appear to say yes. Maybe, like that SUV driver, we in aviation are becoming libertarians. Rules are for somebody else, and if we don’t cause conflict or add risk to others why should arbitrary rules apply to us?

I hope I’m wrong because aviation safety comes from creating and following procedures and norms, arbitrary though they may be.

What do you think?

Posted in Mac Clellan's Left Seat Blog | 41 Comments

Stick Force Is a Safety Issue

The most common cause of loss of control, particularly in amateur-built airplanes, is an unintentional stall. When that happens at low altitude the results are usually fatal. I think one of the most effective ways to reduce the number of those accidents would be to improve control stick force.

Until the end of World War II there wasn’t much investigation into what made an airplane easy and predictable to fly. Airplanes tended to be individuals each with often very different feel on the controls, and response to control inputs.

After the war the NACA–forerunner of NASA–and the military conducted testing to determine what flying qualities made an airplane easy and predictable for pilots to fly. A more predictable airplane lowers pilot workload which is a good thing for the military who wants its pilots to concentrate on the enemy, and for civilians who want to carry passengers as safely as possible.

One of the major discoveries of the research was that stick force–how much force a pilot must apply to the controls to maneuver the airplane–is critical. Stick force is a subliminal cue from the airplane to the pilot to communicate what the pilot is asking the airplane to do, and how the airplane will respond.

Control force and feel is not unique to the airplane-pilot interface. Control input “feel” is important for just about any man-machine operation. For example, remember the power steering systems in cars of the 1950s and early 60s? In most you could spin the wheel with one finger when stopped, or cruising at 80 mph. The controls were totally numb. A driver got no feedback to let him know how the car was responding to his control inputs. Car steering systems have come a long way since those days, but not all airplanes have.

Testing in airplanes showed that the best flying qualities come when force on the ailerons is lightest, pitch force is greater and finally rudder displacement requires the most force. The rule of thumb is that if aileron force is 2, pitch stick force should be 4 and rudder force 6. This ratio is difficult to achieve, but it is a goal and the best flying airplanes come close.

When it comes to controllability, particularly at lower airspeeds, stick force in pitch, and particularly the stick force gradient, are most important for safety, and the hardest to achieve. The pitch force gradient is the increase in force needed to pull or push the airplane further away from its trimmed airspeed. In the best airplane the stick force gradient is linear, meaning the force builds in a steady predictable manner as the pilot deviates from trimmed airspeed.

The reason stick force and a positive force gradient is important to safety is that the force, the feedback if you will, from the controls instantly reminds the pilot he is changing airspeed and wing loading. With a strong positive stick force you know instantly that you are changing the flight profile. You inherently know that when pulling harder while flying at slower airspeed, such as in the traffic pattern, you are treading on thin ice and are loading the wing. When it takes a lot of pull to stall the wing you are more aware of what you’re doing then if you can stall with only light forces on the stick.

Ideally stick force is created by air loads on the control surfaces. But that can be tricky. For many reasons from the design of the control surface to the actual control mechanism stick force gradient is seldom linear, and maybe not even positive. And in small light airplanes the force may be so light that even if it is positive it doesn’t give the pilot the feedback he should have.

In certified airplanes the FAA became ever more demanding of good positive stick force in pitch as the years went by. In an airplane with much of a CG range it is almost impossible to meet the stick force rules without springs to pull against the controls, or a bob weight to resist your effort as the wing loads up.

Early in fly-by-wire control development designers tried sticks that sensed only force, but not displacement. Early F-16s are an example. Most pilots hated that and found it hard to fly. So sticks were designed with spring systems so that as the stick is displaced the springs provide the force gradient even though only an electronic command, not control cable movement, is being created.

Springs, bob weights and other devices to add stick force are missing from most, if not all, homebuilt designs. In fact I almost always hear descriptions of how feather light the control force of a design is and how that makes it fly like a fighter. When I hear that I think yes, like a fighter on the losing side.

Even in extreme aerobatic flying or other precision maneuvering many pilots intentionally fly with the airplane significantly out of trim so they are always holding stick force in pitch. Without the force it would be like driving that 1958 Chrysler.

Angle of attack display systems can help increase awareness of stall margin in light airplanes, but stick force can be even more effective because it is always there and you don’t need to look at a display to comprehend what the airplane is telling you. There is no way to decree how a homebuilt should handle and what its stick force gradients should be, but based on the experience of the standard certified airplanes more positive stick force could help. Finger tip flying is not better  and more controllable than finger tip driving was in those cars years ago. Positive stick force makes for precise and predictable flying.


Posted in Mac Clellan's Left Seat Blog | 19 Comments

It Makes No Sense to Raise Sport Pilot Weight Limit

I still get a pretty steady stream of requests, demands even, that somebody should do something to force the FAA to increase the maximum takeoff weight of airplanes that can be flown by sport pilots or any other certified pilot using a driver’s license as medical certification.

There is a long list of standard category airplanes that are not very far above the 1,320 pound maximum weight allowable for LSA and can be flown to Sport Pilot standards. For example, the Cessna 150 has a max takeoff weight of 1,500 pounds and the 152 is at 1,600 pounds. And the 150/152 is one of the most popular airplanes ever with more than 23,000 manufactured. In 1966 alone more than 3,000 were built.

There are many other basic two-seaters that would meet the light sport rules if the maximum takeoff weight were increased just a couple hundred pounds. Some, like the Ercoupe series, are so close that a few models fall into the category, while others miss by just a few pounds.

What difference can these small increases in weight above the 1,320 maximum for sport pilot flying in landplanes make?

Well, a weight limit, along with maximum cruise speed and stalling speed, were always part of the discussion when the light sport category and sport pilot were created. The operative word is “light.” The 1,320 pound limit is a general consensus of what other nations had done in creating basic light airplane certification categories. The odd number of pounds was selected because it is very close to the 600 kilo limit that is used elsewhere. Because a stock J3 Cub, the iconic light airplane, fits under the weight it’s hard to argue that the max weight limit is too low for a basic light airplane.

A truism in flying is that the cloud tops will always be at least 100 feet higher than you can climb, and no matter how much range an airplane has there is at least one trip you want to fly that is just a little longer. Same goes for the LSA weight limit. No matter where, within reason, the limit is set, there are airplanes that will weigh just a little more.

I am not calling for the FAA to increase the weight of standard category airplanes that can be flown to the Sport Pilot rule because there is a better solution, and that is third class medical reform. Though progress is much slower than we like, change is coming. There is a rule proposal in the pipeline and we should see it soon. Nobody outside of government yet knows exactly what the proposed new rule will say, but everyone believes that when it is adopted flying a wide range of piston airplanes under VFR in the daylight will be allowed using a driver’s license as medical certificate.

And the driver’s license as medical is the only meaningful change that a weight increase for LSA would allow. A standard category airplane flown by a sport pilot must still meet all the other maintenance and registration rules that apply to heavier airplanes. An airplane that weighs 1,320 pounds or less isn’t re-certified into a new category when a sport pilot flies it. It’s only the pilot privileges that change.

So it makes no sense to badger the FAA about increasing the standard category sport pilot weight limit because a much better solution that we all want is in the works. I can only guess what the third class medical changes will be, but I’m ready to bet a few bucks that you will be able to fly a much more capable airplane than a Cessna 152 with driver’s license medical certification before too long.

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

Will Avgas Prices Follow Crude Oil Plunge?

Crude oil prices have plummeted more than 30 percent over the past week or two. Auto gas has already dropped to a national average pump price below $3 a gallon, something not seen in years. Will 100ll avgas prices also drop?

The answer is that eventually avgas price into the wing will come down. But it won’t drop as much as the price of crude, and avgas retail prices won’t mimic every swing in crude prices.

Crude oil costs are a big component of the retail price of avgas, but in most cases crude isn’t even a majority of cost we pilots pay. Avgas has become a boutique product because it is made and sold in such tiny quantities, and it has so many unique and specific requirements. Avgas volume has slipped so far and the complications of making it and delivering it are so great price simply doesn’t respond very much to market forces, or even to the cost of components such as crude oil.

A useful way to think about avgas and crude oil prices is to compare it to charcoal lighter fluid. Both are petroleum based products, but nobody expects the price of a jug of lighter fluid to drop more than 30 percent just because crude oil prices have.

The final price of lighter fluid involves packaging, shipment, storage and retail costs in addition to making the fluid itself. And the sum of those costs are certainly higher than the value of the crude oil used to make the basic fluid. It’s the same for avgas.

Avgas sales volume is so low that many FBOs receive shipments only once every several months. So no matter what happens to prices between shipments that FBO has to recover what he paid for the avgas in his tanks. And credit terms from fuel companies are very short so the FBO has already paid for the load of fuel long before he recovers his cost through sales.

Because of the absolute need to prevent contamination of both the fuel and the shipping containers it is very difficult to transport avgas. Often dedicated barges or tankers are used so the lead doesn’t contaminate other products that could be loaded later. In some cases many months worth of avgas are shipped to a region in a single delivery. For example, barges carry the entire winter months supply of avgas to many of the northern tier of states. If avgas production prices change it won’t matter because the fuel was made and delivered long ago.

On the other hand car gas is a commodity that responds to all cost forces almost by the minute, and certainly by the hour or by the day. Jet fuel is the same. Because of delivery and storage expenses jet fuel at an FBO will always be higher than what major airlines can buy from pipelines linked directly to the airport, but still, jet will come down soon in response to crude price declines.

Another wrinkle in the crude price plunge surprise is what will happen with the lead-free avgas replacements the FAA is now beginning to test? The companies that have submitted the potential avgas replacements have all said the price of their formula would be “competitive” with 100ll. But they were saying that when crude was above $100 per barrel and had been there for years. Will low crude prices leave a replacement fuel priced far above the cost of 100ll? Since the proposed fuel formulas, how they would be made and by what refineries, and everything else is all secret, there is no way to know.

When I talk to people who actually provide aviation fuel they say if you want to worry about something worry about supply disruption, not price. And they say that even about jet fuel. The national infrastructure to deliver aviation fuel is so decrepit and inadequate that a steady supply of fuel even to major airports like JFK can be threatened as we saw this past summer.

So, we all welcome the new prices at the gas station but can’t expect an equivalent drop in avgas prices, or charcoal lighter fluid for that matter. We avgas users are just too small in number to have the clout that free markets respond to.


Posted in Mac Clellan's Left Seat Blog | 19 Comments

Pushing Nature’s Airspeed Limits

The Aerion Super Sonic Business Jet

For decades we’ve made no significant gains in useful airspeed. The reason is nature’s speed limit, the speed of sound, Mach 1. But now there is some progress.

Exhibit A is the Gulfstream G650 which cruises efficiently at Mach .90, about 516 knots true airspeed. That’s more than 50 knots faster than the high speed cruise of other jets. Even the G650 long range cruise at Mach .85 is an advance of almost 30 knots over the high speed cruise of other jets.

Gulfstream has been able to push the speed limit forward through a better understanding of how air flowing at transonic speeds behaves, and how to design an entire airframe to minimize the drag of the inevitable shock waves.

Now we are seeing increased interest and investment in the dream of a supersonic private airplane. Aerion has been working on a supersonic airplane for more than a dozen years but has new capital, and new credibility, now that aerospace giant Airbus has made a significant investment. If Airbus believes an SSBJ is possible and is willing to invest should we believe?

Aerion’s chief aerodynamicist Richard Tracy holds patents on a natural laminar flow supersonic airfoil. That seems like a non sequitur. Supersonic flow is the opposite of laminar flow which is smooth and non-turbulent. As airflow reaches transonic speed a powerful shock wave builds which retards all airflow like a dam.

How could anything like smooth laminar flow be maintained at supersonic or even transonic speeds? That’s the Aerion secret, and it has worked in wind tunnel and actual airfoil testing in flight. And it’s what Airbus wants. Even if Airbus has no interest in building a supersonic airplane of its own it has huge stakes in reducing drag as airflow over its conventional airframes reaches transonic speeds even when the airplane itself is flying at Mach .80 or .85.

The speed of sound is also a very real speed barrier for propeller airplanes but we are seeing some progress there, too. Mach 1 places its speed limit on prop airplanes mainly by robbing the propeller of efficiency beyond a certain airspeed. The airspeed a propeller blade encounters is a combination of the rotational speed and the airspeed of the air entering the propeller disk. Once that airspeed goes transonic the same shock waves the hold back a jet airplane rob the prop of efficiency. No matter how much more power is applied to the propeller Mach effects restrict how much thrust it can deliver at higher airspeeds.

Unlimited Reno racers prove that a prop airplane can fly very fast, in excess of 500 mph. But they achieve those speeds at very low altitudes. Mach value increases as air temperature warms so a Reno racer flying at 500 mph in the warm low altitude air over the race course is flying at only about Mach .65. That’s fast, but still modest by jet speeds. And if the Reno racer climbed to an altitude where cruise can be efficient the speed would plummet because the airspeed value of Mach goes down and the propeller is laboring at a higher percentage of Mach.

But, again, we are seeing progress, namely in the very thin and swept prop blades Hartzell is making. It’s been known for decades that a thin airfoil and swept leading edge delay shock wave formation to a higher speed but until very strong composite fiber material was developed there was no way to make a propeller blade of the optimum shape. Now Hartzell can do it, and propeller airplanes like the TBM 900 are flying faster on the same amount of engine torque.

While we can see progress in pushing back nature’s speed limit there is an artificial limit that remains–laws against supersonic flight over land. The U.S. and many countries around the world forbid supersonic flight because of the unavoidable sonic boom. To be useful and worth the $80 to $100 million a supersonic private airplane would cost you need to fly supersonic over land, not just oceans.

At this point it’s difficult to know if nature or manmade laws are holding back development of a supersonic airplane. Gulfstream has invested in technology to suppress a boom but says it won’t go all-out until laws change and allow supersonic flight over land. Aerion believes it can quiet the boom and thus fly around the laws. Either way, legal as well as aerodynamic hurdles remain.

For those of us who marveled at the sleek models of supersonic jets built by Douglas, Boeing and others, and the exotic Concord built by the British and French, it’s sad to see those dreams of our youth still stuck on the shelf. Maybe nature has simply thrown up too big of a road block to fly efficiently with useful range at supersonic speeds. But maybe not. I didn’t believe I would be around to see an airplane cruise for more than 5,000 nm at Mach .90, but Gulfstream did it. Maybe our best minds can find ways to push nature back and resume our long delayed march toward ever faster and useful airplanes. I hope so.

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

Flying Fun With Your Tie On

When I started at Flying Magazine nearly 40 years ago we always wore neckties to go flying. And usually suit jackets or blazers.

And we weren’t the only ones. The pilots from Cessna, Beech, Piper and the others all knotted up the tie to go flying. It didn’t matter if we were in a Cessna 152, a Piper Aztec, a Beech King Air or a Cessna Citation the tie was standard equipment.

I thought about that here at the National Business Aviation Association convention and show in Orlando this week. Most people walking around the vast exhibit hall and even out at the airplane display at Orlando Executive airport have ties and jackets on.

I think the reason we all dressed up to fly a Skyhawk or Cherokee all of those years ago was to elevate the image of private flying. The industry we were all part of very much wanted to be taken seriously. Private airplanes were gaining capability and could deliver all sorts of transportation value. And professionalism, no matter what you flew, was everyone’s goal.

At the time I remember chaffing about the neckties on a 100 degree day in Wichita wondering why we couldn’t dress more comfortably. But we were all in it together so while we may have questioned the value of the ties I don’t know any pilot who would trade the tie for the chance to fly.

And I remember the flying was lots of fun. We were turned loose with brand new airplanes, sometimes airplanes that had not yet been fully tested and certified. New models were being developed regularly and personal aviation was booming. It was a peak of development and sales activity we haven’t seen since.

So walking around here at NBAA with my coat and tie  I’m reminded that fun flying comes in all forms. It’s hard to beat a Cub on a sunny day with the door open and the slipstream flapping everything but a necktie. But then the guys who get to fly the new Gulfstream G650 at Mach .90 for more than 5,000 miles are having one heck of an experience with the tie firmly in place.

Oshkosh and NBAA couldn’t look more different. And though many pilots attend both shows they couldn’t look and dress more differently for the two. But in all cases flying is still fun no matter what the airplane is and how you dress to fly it.

Business casual has become the norm for most private flying. Even at Gulfstream and other business jet makers many wear business casual, especially during the hot months.

Maybe all those years ago the neckties demonstrated we were serious about flying, professionalism and safety. Perhaps we needed those ties then. And no matter what the ties didn’t sap any of the fun out of flying.

Now we dress to suit the occasion, the mission, and even the expectation of our passengers. That makes more sense. But I’m glad I got to fly through the mandatory necktie phase and hope that our dress helped the cause in some small way. And to get a chance to fly an interesting airplane I’m happy to wear whatever is required.

P.S. I was just reminded by an astute reader that Orville and Wilbur wore ties, too. Looks like it’s neckties two, silk scarves one.

Posted in Mac Clellan's Left Seat Blog | 17 Comments

Total Airplane Rebuild vs. Repair

Cessna assembly line from

Over the decades that I have been flying in and writing about private aviation the concept of remanufacturing airplanes has waxed and waned. Now the idea of remanufacturing existing airplanes is waxing again. From Cessna 152s to business jets there are now many projects to make old airplanes as good as new.

At first I bought into the remanufacturing concept. Disassembling an airplane to its barest of stud walls and then replacing just about everything seems to make sense. The components that wear or crack or corrode are gone so the rebuilt airplane should be as good as new, right?

Well, first of all, a brand new airplane is far from the most reliable. When everything, or almost everything, in an airplane has been touched, moved, installed, adjusted and tinkered with by humans the number of things that can go wrong is almost infinite. After all, that’s why prudent airplane owners insist on test flights after even pretty basic maintenance procedures, much less a total remanufacturing.

But once the totally rebuilt airplane is debugged won’t it be more reliable? I once believed that, but not anymore.

I’ve either been lucky, smart in selecting shops, or perhaps a careful observer, but I don’t need the fingers of both hands to count the number of trips in more than 5,000 hours of flying my Baron that have been delayed or scrubbed because of a maintenance failure. Yes, I have flown a few trips without some non-essential equipment functioning, but even those have been pretty rare.

The few what I would call “major” maintenance or mechanical failure issues include an engine throttle body that cracked leaving a big hole on the wrong side of the throttle plate so the engine quit at idle on taxi in, and the other was a jammed oil pressure controller that wouldn’t regulate pressure properly on takeoff after the engine oil warmed up. Both of those events happened to fairly low-time engines so an airplane rebuild wouldn’t have prevented them.

The other events that caused the rare delay or scrub all involved accessories. Once a starter failed without warning causing a delay of a few hours. The same for a magneto. I had a propeller spinner bulkhead crack but the spinner was much newer than the airplane. I’ve had an electric standby fuel pump fail. And I’ve lost count of the number of alternators and vacuum pumps replaced. Those things are like light bulbs. It’s impossible to know for sure how long they will last.

On the other hand, the significant airframe issues I’ve encountered didn’t delay flights because they were found at annual. For example, the far aft bulkhead, the one that supports the vertical and horizontal tail spar loads, was found, at annual, to have a small crack. The crack was so small it’s presence could only be confirmed by having one mechanic wiggle the horizontal while the other used his finger to feel for the crack. The crack would have eventually been serious if not found and the bulkhead replaced. And a total airframe rebuild would have found that crack. But so did the annual.

I also had a crack in the magnesium elevator, a not rare event in Barons. The crack wasn’t there, and then it was. Could a total airframe remanufacture predict the crack would form? I don’t see how.

This is a sermon that Mike Busch has been preaching to airplane owners and aviation maintainers for years. We don’t get any credit, any benefit, or more safety and dispatch reliability by replacing stuff that is still airworthy. And airworthy isn’t the same as new. It’s something that is within the tolerances of the type design.

Old airplanes are great values. New avionics add enormous capability and convenience. Often there are STCs to update the propulsion with a better engine and propeller. And new paint and interior can make an airplane look like new.

But as for stripping an airplane to the bare bones and then rebuilding it to make it more reliable, I don’t think so. Inspect carefully, fix what wears and breaks, and spend what you can afford on avionics and cosmetic upgrades and you can enjoy enormous value from older airplanes.

What do you think?

Posted in Mac Clellan's Left Seat Blog | 24 Comments