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 | 3 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 | 16 Comments

Total Airplane Rebuild vs. Repair

Cessna assembly line from kansasmemory.org

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

What’s Missing in PIREPs–Good News

When the weather forecasts contain the chance of some iffy conditions I bet you’re like me and study the pireps. Forecasts are helpful, and more often accurate than not, but what I really want to know is what’s it like up there. And only a pilot in the air can tell us.

But often when the weather is questionable there just aren’t many, or even any, pireps. Especially at the lower altitudes where we pilots of unpressurized airplanes do battle with the weather.

When there is no pirep it probably indicates a couple things. If the weather is really awful the absence of pireps can mean nobody is out there flying, particularly in the lower levels. I don’t know how many hundreds or thousands of times I’ve asked controllers about the ride ahead only to be told that nobody went through there at my altitude for hours. Being a pioneer can be adventurous, but too much adventure is a bad thing.

The other likely explanation for an absence of pireps is that the weather is just fine, much better than forecast.

I don’t know why we pilots behave this way, but when things are going great we just don’t want to talk about it. Have you ever heard a hangar flying story about hundreds of miles of blue sky and perfectly smooth air? Me either.

So when we launch into an area forecast to have turbulence, or rain, or low clouds, or ice or thunderstorms and don’t find that bad stuff we heave a sigh of relief and thank the weather gods. And we don’t mention it to anybody outside the cockpit. Meanwhile, the pilot on the ground trying to decide to takeoff into the poor forecast has no idea that the forecast is wrong and he can have a good trip.

Airline and business jet pilots are better at passing along the good, as well as the bad news about flight conditions. For example, when turbulence has been forecast, or reported earlier, it’s common for a jet pilot to check in with the controller after a frequency handoff and announce “smooth ride” or words to that effect without being asked. Other pilots on the frequency hear that it’s smooth at that altitude, and controllers pass the information along to other control sectors.

A few years ago the FAA made a concerted effort to remind controllers to collect icing reports when ice was in the forecast. Icing is notoriously difficult to forecast and is usually very localized. Until and if progress can be made in icing forecasting passing on pilot reports promptly is the best way to keep pilots either still on the ground or already in the air out of the icing.

I live and fly in ice country here in the lee of Lake Michigan and any day that it’s cloudy and cold–which is many days–controllers always ask if I found ice. They also ask about the air temp, cloud tops or layers and type of ice. That information turns into a pirep that goes into the system quickly, and controllers in that sector or nearby sectors pass it along to others. Ground and tower controllers also relay the ice information to pilots still on the ground.

The FAA emphasis on icing information is helping, at least I find it very helpful. And perhaps the most important aspect of the icing reports is when there is no ice, which is more often than not the case. It’s absolutely as important to know that ice isn’t there as it is to know where the ice did appear.

If you fly IFR or with radar flight following it’s extremely easy, almost automatic, to make a pilot report. All you need to do when there is a little lull on the frequency is tell the controller your flight conditions. Controllers key the info into the system so it shows up on the FAA weather network, and also verbally relay the report to other pilots and other controllers. You don’t need to wait for the bumps or ice to tell the controller. Let them know–so they can tell the rest of us–when things are going great, too.

It’s a little more complicated for the VFR pilot to make a pirep because he has to find a usable frequency to raise FSS and then make a more formalized report. I don’t know why this is true, but the radar controllers can gather the important information quickly and without any rigmarole but the same pirep is something of a production with FSS on the radio.

But, the bottom line is that if there were any questions in the forecast only pilots in the air can answer them. Good news, the forecast is wrong, is every bit as important and useful as bad news. Please share.

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

Cirrus Fully Embraces the Chute

When the Cirrus SR20 entered service as the first production airplane to have a whole airframe recovery parachute as standard equipment about 15 years ago aviation insurance underwriters didn’t know what to do.

The underwriters–and actually most of us in general aviation–expected Cirrus airplanes to be raining down under the chute but nobody knew how much damage the event would cause or how much it would cost of fix the airplane. Because of the chute underwriters just didn’t know how to price Cirrus hull coverage.

As it turned out the underwriters didn’t need to worry. Cirrus pilots did have accidents but for all of the conventional reasons but they just weren’t using the chute. Early on there was an engine failure in a Cirrus but the pilot shoehorned the airplane into a small clearing instead of pulling the chute. That surprised most of us. The chute just wasn’t much of a factor even in accidents where it seemed it could have saved the people onboard from death or serious injury, or at least greatly increased their odds of a successful outcome.

But finally that situation is changing. More than 95 people are alive because Cirrus pilots deployed the Cirrus Airframe Parachute System (CAPS) and the number of deployments  is increasing. I give Cirrus and its new training system all of the credit for the changing attitude among pilots toward the chute.

CAPS was and still is a foreign concept for traditional GA flying and the pilot training system. The mantra in GA remains “Fly the airplane, Fly the airplane.” That is the opposite attitude needed to make full and effective use of CAPS. With a CAPS the mindset must be when in doubt deploy the chute now. No waiting allowed, or trying to continue to fly the airplane.

The military learned this decades ago when ejection seats were invented. For the seat to do any good a pilot needs to have ejection way up near the top of the memory items for most emergencies. If something goes wrong, or you’re hit, wasting time trying to figure out what went wrong and how to fix it can rob a pilot of any chance of a successful ejection.

In GA we have tried to instill a similar type of thinking in pilots who fly piston twins. For example, if an engine fails close to the ground on takeoff your chances are so much better if you pull back the other engine and land straight ahead instead of trying to continue the takeoff on one engine. It’s a mindset a piston twin pilot should have and needs before he starts the takeoff roll.

It’s the same with CAPS. In fact, the CAPS can do essentially what the second engine does for a piston twin pilot. CAPS can’t save you from crashing fatally in every emergency situation. But, as with the piston twin, the periods of exposure on each flight where the other engine or CAPS can’t save the occupants are brief.

For example, CAPS can deploy successfully as low as 400 agl in level flight. On takeoff a Cirrus pilot needs to constantly be thinking that when he climbs through 400 feet the chute is there and ready to go in case anything goes wrong. That’s about the altitude where a piston twin pilot is likely to have success continuing if one quits on takeoff. CAPS will not continue the takeoff, but is very, very likely to save the occupants from serious injury. The current Cirrus training program is hammering this CAPS planning home before every takeoff.

Engine failure or some other serious structural or system problem are obvious reasons to deploy the CAPS, but there is still work to do in convincing Cirrus pilots to pull the chute anytime control is in doubt. That is especially true when flying in the clouds.

If a pilot ever becomes disoriented in the clouds it is virtually impossible to regain control. The reason you have vertigo and lose control is because you can’t comprehend what you’re seeing on the instruments. Or some instruments have failed and you can’t figure out which. As the airplane deviates further from controlled flight the instrument display will become increasingly incomprehensible. The “level” button on the newest autopilots can help, but CAPS can save the confused pilot in IMC when nothing else will.

Cirrus is pounding away on these issues in its new training program in much the same way every jet pilot is trained and tested to be ready to handle an engine failure at the worst possible moment on every takeoff. It’s a big job to turn around nearly a century of instructors telling pilots “Fly the airplane, Fly the airplane” and make the decision to stop flying, pull the chute, and live to fly another day.

It’s impossible to know specific accident rates because we still don’t know how many hours are flown and under what conditions, but the Cirrus accident record is definitely improving, especially the fatal accident record. I give the company credit for fully embracing the CAPS and moving it to the top of mind for Cirrus pilots. “Fly the airplane” is still the best advice for the rest of us, but for Cirrus pilots CAPS is the best answer for most emergencies.

As for insurance costs I think underwriters have figured out a CAPS deployment is a lot better than a fatal accident. And now more pilots understand that, too.

Posted in Mac Clellan's Left Seat Blog | 31 Comments

Early Fall, The Best Time to Fly

Astronomical fall season has just begun, and for most parts of the country this is the best flying weather of the year.

Variability and changeability is what makes weather weather, but on average the first five or six weeks or so of fall are the most benign and bring the best flying weather.

Weather–at least the components of weather we care about when flying–is caused by contrasts in parcels of air. For example, air in an area of high pressure rushes into a low pressure causing wind. The greater the difference in pressures the stronger the wind.

Contrasts in temperatures also cause air to move rapidly causing wind and turbulence. Add moisture to the mix and you have the fuel for cloud formation and precipitation. The colder the air moving in behind warm moist air the worse the flying weather will be.

Late fall and spring usually bring the worst flying weather. In both late fall and spring the overall weather patterns are making their seasonal shifts and contrasts between systems are great. In the northern latitudes November is often the worst month for unsettled weather with deep lows and strong highs clashing to create powerful winds, layers of clouds and all manner of precipitation. In the southern climes early spring can be most violent as the warm air and spring moisture arrive and destabilize the cooler air of winter causing huge thunderstorms and tornadoes.

But for now, early fall, there is generally stability in the atmosphere. Night and day are of equal length so the cool evenings and warm afternoons tend to offset the destabilizing effects of extreme temperatures. Unlike a sunny spring or summer day you can often find smooth air even when the sun is warming the ground. In the evenings breeze generated by the warmth of day often dies down to nothing but there is still enough daylight left to at least shoot some landings in the stillness.

And the best thing about fall flying is the view for most of us. While ground pounders are left to ooh and awe from their car windows we can look down at a riot of fall colors. On the ground people see a few trees and golden leaves but from our perch we can see hundreds, even thousands of trees changing colors. We can also see how different species of trees respond to fall with an array of hues and at a different rate. It’s also possible to see how even small changes in elevation cause the trees to turn differently leaving stripes and patches of color those on the roadside can never see or marvel at.

Fall also brings something we all need in life–a deadline. When fall arrives we know the time left for good flying before winter blows in is short. Of course there is no need to lock the hangar door when winter arrives, but for most of us winter flying can be more chore than pleasure. We can seize each beautiful early fall day and spend it in our airplanes knowing we have made a wise investment against the dark days of winter just ahead.

Even though fall flying can be best, it’s still playing the odds. A gale blew through here over the weekend building waves 10 feet and higher on Lake Michigan and bringing layers of rainy clouds. Gordon Lightfoot got it right. When the gales of November come early no craft on the water or in the air is safe.

But the gale blew itself out and just as fall began on the astronomical calendar the forecast became perfect. Highs around 70, winds of 10 knots or less, a few scattered clouds as far as the 10 day forecast can see.

It’s time to go flying.

Posted in Mac Clellan's Left Seat Blog | 3 Comments

Aerobatics Versus Flying IFR

I was chatting with the impossibly energetic Sean D. Tucker at Oshkosh this summer and was, as usual, knocked over by his schedule. In addition to flying a bunch of air shows and devoting endless hours to being chairman of EAA Young Eagles, he was running around the world to climb extremely tall mountains.

To that list Sean told me he wanted to add learning to fly IFR. For all of his thousands of hours in the cockpit Sean does not fly IFR. And he is afraid to fly in the clouds. He told me it just flat out scares him not to be able to see the ground or the horizon.

For many of us who have watched Sean fly in every imaginable attitude–and some unimaginable to me–very close to the ground the idea that flying in the clouds frightens him is a surprise. But I have heard that from other air show performers. They just don’t like being in the clouds, and many simply won’t do it.

There are exceptions, of course. Gene Soucy comes to mind. Gene has been flying aerobatics and air shows for decades, but he also flew a career with the airlines which is totally instrument flying. Gene had even rigged up a set of removable IFR instruments in his Christen Eagle so he could punch into a cloud when necessary while trying to ferry his airplane from show to show during the many years he was part of the Eagles team. But Gene is something of an exception.

The thought of tumbling through the air in one of those gyroscopic maneuvers Sean and others have perfected scares the crap out of me. But, for me, flying into a cloud seems as ordinary as raising the landing gear. Why the big difference?

My guess is that the top aerobatic pilots like Sean almost never look inside the cockpit. When you watch those many “hero cam” videos of them flying their routine the head is in constant motion. They look rapidly from side to side at the wing tips. They throw their heads back to see the horizon and the ground which is not in its usual place. They even sometimes look straight ahead, but only briefly, and not at the instruments.

In aerobatics the view of the horizon and the ground is everything. That’s why many who fly competitive aerobatics put those protractor devices on the wingtips to visually line up the attitude angles with the horizon.

In instrument flying the horizon is also critical, but it’s artificial. The objective is to keep the airplane close to level. The maximum bank angle used in conventional IFR flying is 30 degrees. The goal is to constantly compare the indications from the primary flight instruments to stay on course, altitude and target airspeed while moving your head as little as possible. The big, abrupt head movements aerobatic pilots make are the perfect setup for vertigo when flying in the clouds.

Obviously military fighter pilots learn to fly all sorts of unusual attitudes based only on instruments so it’s not an impossible task. But even the Thunderbirds and Blue Angels don’t fly the extreme maneuvers that Sean and the other top air show pilots routinely fly.

I guess it all comes down to each of our own comfort zones. I see that Sean has checked off another of his mounting climb goals, so maybe IFR flying is next on the list. One thing I know for sure is that Sean has about a 1,000 percent better chance of becoming comfortable flying in the clouds than I do flying any part of his routine

Posted in Mac Clellan's Left Seat Blog | 12 Comments

Finally, A Real Life Test of an Oil Additive

Most of us grew up in the age of STP and Marvel Mystery Oil. And there were dozens of other potions that, when dumped into our engine’s crankcase, increased horsepower, eliminated wear and were even likely to make you more attractive to girls.

Each miracle additive had its supporters, and they all had reams of “data” showing exactly how much benefit they delivered. Which additive was best and exactly how it worked its magic was fodder for endless discussion among those of us who cared about engines, power and speed.

We’ve seen fewer miracle engine oil additives in aviation, probably because unlike the automotive world, flying is regulated. But regulation never totally stopped airplane owners or mechanics from slipping in a slippery substance they were convinced made things better.

But regulation of aviation engine lubricants is odd. There isn’t an FAA specification for lubricants. In general, if the engine manufacturer approves an oil for use in its engines then the FAA agrees.

Aircraft piston engine lubricant specs that do exist are based on military specs developed in decades past before the Navy and Air Force transitioned to turbine power. These “mil specs” are a solid foundation for creating a lubricant, but they haven’t been updated in many years because the military no longer has a requirement.

It is possible to get an FAA STC for an oil without also earning the stamp of approval of the engine makers. But if the engine manufacturer refuses to bless the oil, or an additive, the engine owner can be left in limbo if problems arise.

Piston airplane owners, and more often their mechanics, are wary of new oil formulations. Even a technology as tried and true and many decades old as multi-viscosity is not trusted by all in aviation. Many mechanics and engine overhaul shops are firmly convinced that only single grade oil can protect their engines, and a few shops absolutely insist that only that oldest of old fashioned lubricants be used.

Oil companies have tried to introduce new lubricant technologies with mixed success. About 30 years ago an all synthetic oil held great promise to reduce wear and oil consumption and I had terrific experience with it in the Bonanza I owned then. But the synthetic wasn’t good at suspending the sludge created by an air cooled engine burning leaded gasoline and many owners had problems. The oil, even though approved, and even recommended, by engine makers, was withdrawn.

The biggest problem with any lubricant is that many piston engines develop problems prematurely. When that happens something must be blamed, and the oil is near the top of the list of suspects. So if an engine runs smoothly on to TBO and beyond whatever oil was in there is praised and credited. That’s one reason why single grade oils fly on when they have been abandoned years ago by other piston engine operators even though a multi-weight oil likely would have had the same results.

So, for all of these reasons I’m very happy to see that Continental Motor Services (CMS) and Aircraft Specialties Lubricants (ASL) have gotten together to conduct a structured test of CamGuard, the oil additive ASL has produced for several years. CMS is the old Mattituck which is the division of Continental that installs, repairs and maintains engines and airplanes.

ASL claims that CamGuard helps prevent engine corrosion which is particularly destructive of the cam lobes and lifters. The company also says the additive reduces wear, retards internal deposit buildup and helps prevent “scuffing” of moving metal parts during engine start. In other words, CamGuard claims to do everything everyone of us piston engine owners wants.

CamGuard is “accepted” by the FAA so you’re not breaking any rules by using it. But as far as I know neither Continental or Lycoming have officially endorsed the additive one way or the other. That’s why I find it so encouraging that Continental is conducting this study to collect objective data in real world use.

Airplane owners who have had engines overhauled or repaired by CMS can join the study. The owners will supply an oil sample at each oil change, and some of the engines will undergo “enhanced” inspections looking for signs of wear, corrosion and so on. The study will cover the 18-month warranty period on the engine.

I’m really looking forward to the results of the study and I hope they are conclusive one way or the other. We are surrounded by myth and superstition when it comes to aircraft engine oil, and I hope we can finally see real convincing results to guide us. There have been laboratory tests, but this is real world flying.

Stay tuned.

Posted in Mac Clellan's Left Seat Blog | 13 Comments

FAA As Hangar Use Tiebreaker

The FAA has issued a policy statement reinforcing its stance that hangars on airports that receive federal funds must be used for aeronautical purposes. That makes sense. But the rub is what constitutes an aeronautical use.

The goal of the FAA policy is to prevent people from using hangars for non-aviation purposes and forcing an active airplane out into the weather. That’s great. Who wants to leave their airplane outside while hangars are stuffed full of boats, motorcycles, recreational vehicles, furniture, whatever because the hangar offers cheaper storage.

But the FAA policy should only be used as a tiebreaker.

What shouldn’t be governed by FAA policy is use of privately owned hangars. In general it’s not possible to buy property on a publicly owned airport so people who want to build their own hangars for personal or business use lease the land. In the typical arrangement the private owner bears the cost of building and maintaining the structure and at the end of the land lease ownership of the actual hangar building reverts to the airport.

The airport authority and the private hangar owner can make their own deal with use stipulations when the lease is negotiated. The FAA should have no say in that agreement. If the airport authority doesn’t like the deal it can change it when the land lease eventually expires.

The other circumstance where the FAA should stay out of airport business is when, as is increasingly common, there is an excess of hangar capacity. At many airports where 10 years ago the best you could do was get on a hangar waiting list there is now an oversupply. I know at my airport not every T-hangar is rented, and the airport authority hasn’t raised rents in many years.

When a hangar is empty and no airplane owner wants to rent it the airport authority should put the space to the best possible use. Empty hangars can store airport equipment, or maybe even bring in much needed funds by renting to somebody who wants to store something other than an aircraft. So long as no airplane owner is left out in the weather, an empty hangar should be put to use in whatever way is most effective for the airport.

But what about the circumstance where there is a hangar shortage and not every airplane owner who wants to move his airplane inside can rent space? Let’s say you just bought an airplane new to you, or finished a many years long building project and your pride and joy is forced outside. But in a hangar somebody else has his boats, cars and other stuff and no airplane. Or how about the person who is on the fourth year of building the horizontal tail of his project, a task that would fit in a single-car garage? Should your actively flown airplane be left out of hangar space being used by people who don’t have an active airplane?

It’s a tough situation. Maybe the hangar tenant used to fly and intends to buy another active airplane and doesn’t want to give up the space. Or maybe the tenant just likes having all of his stuff inside, even though that stuff isn’t an actively flying airplane. Those people are very much in love with their hangar deal and don’t want to give them up.

That’s where I see the FAA policy as a tiebreaker. If you have an actively flying, in license airplane and can’t rent a hangar on a public airport, but some hangars are being used by people who don’t have actively flying airplanes, I think the FAA should come down in favor of the airplane owner who flies.

That’s why it’s important that the FAA policy now specifically says that final assembly of a homebuilt airplane is an aeronautical use and won’t be forced out of a hangar. The scope of final assembly of most airplanes needs to be done in a hangar. The policy offers
protection for builders that was never specifically stated before.

And the FAA policy also favors the actively flying airplane owner. When there is a hangar space crunch the airplane flying and using the airport should get the nod.

Overall the FAA policy won’t matter one way or the other to most of us. At many airports hangars are emptying out and few airport managers are going to be looking to toss tenants when they already have unrented space. But at those airports where demand still exceeds supply the nod should go to the owner of the actively flying airplane. Breaking the tie is what the FAA can do.

Let me know what you think.

Posted in Mac Clellan's Left Seat Blog | 16 Comments

Pilots Killed Piston Engine FADEC Advances

An almost universal lament among pilots is that we are flying piston engines that use decades old technology. That’s not entirely true, but you would be hard pressed to find a magneto on any other type of piston engine still in production.

Continental spent a ton of dough to change that situation starting in the late 1990s and its efforts were shot down. Not by the stuck in the mud regulators at the FAA, but by pilots. The very people who say they want technology advances.

The really big improvements in other piston engines such as those in cars and trucks have come from computer control of the entire engine operation. Automated and constantly adjusting control of ignition and fuel have made automotive engines more efficient, more responsive, easier to start, more drivable and more durable. Why can’t we have that in our piston airplanes?

In aviation we call computerized control of an engine full-authority digital engine computer (FADEC). The term came from the turbine engine world where redundant computers were handed the job of controlling fuel flow and other operating parameters to set power, and more importantly, always keep the jet engine within operating limits. I can’t think of a jet in production that doesn’t have FADEC engines.

Before FADEC pilots of jets would be charging down the runway gently moving the throttles to try to find a target fan rpm (N1) or engine pressure ration (EPR). Move the levers too much and you could overspeed and damage the engine. If you don’t move the levers far enough the engines don’t put out the expected power and takeoff performance suffers. Just when a pilot should be monitoring directional control and critical systems during takeoff roll in the pre-FADEC days we had our eyes glued to a couple gauges while we doinked around with the power levers.

Operating most piston engines doesn’t demand quite as much attention, but mismanagement of the controls can damage the engine, or result in less power than expected. FADEC can simplify piston engine operation to nothing more than moving a lever just like stepping on a gas pedal. FADEC would automatically optimize the mixture for all atmospheric and operating conditions to gain maximum engine performance and efficiency while also protecting the engine from the pilot who can use the engine controls in a damaging way.

A big hurdle on the way to piston FADEC was an uninterruptible electrical power source. The traditional piston engine with its magnetos and carburetor or mechanical fuel injection operates with total independence from the aircraft electrical system. And that’s good. Many piston airplanes have very rudimentary electrical systems, and more importantly, have only one of them.

At first it looked like only airplanes with totally redundant transport aircraft type electrical systems could use FADEC. To install the Porsche PFM engine Mooney created such an electrical system. The electrics worked OK, but the engine didn’t pan out.

But Continental was successful in convincing the FAA that a FADEC backup battery could do the job. FADEC doesn’t use that much power so it’s not hard to have a constantly charged dedicated battery with enough power to equal the fuel endurance of the airplane. If the main electrical system failed totally the backup battery would keep FADEC and the engine running until the fuel was gone.

There were several fits and starts on the way to FADEC certification. But Continental succeeded, first in naturally aspirated engines, and then for the turbos. I flew several iterations of the system and the final go worked very well. Just push the throttle and let the computer manage the engine. I even had the magnetic pickups installed on an accessory gear in my new engines in 2000 in the certainty that I would be converting to FADEC before long.

But Continental needed an airplane manufacturer to really launch FADEC. A logical target was Beech with the Continental powered Bonanza and Baron. Beech engineers loved the idea. Beech customers hated it. When Beech asked prospects they learned that not only didn’t sales prospects want FADEC, many wouldn’t buy an airplane with the system.

The problem was mixture control. Many, even most pilots, thought they were smarter than the FADEC computer. They wanted to run lean of peak or rich of peak, or somehow set the mixture to suit their conviction of how it should be done. FADEC, on the other hand, would run lean of peak  under some power settings and conditions, but then switch rich of peak for other conditions. And it did this without considering pilot opinion, only what testing showed was optimum for the engine.

So FADEC, fully developed and certified, faded away. Pilots who demand new technology, it turns out, don’t really want it if it interferes with lore, superstition, and years of experience.

It’s interesting that this is not an issue in some newer design engines such as the Rotax that doesn’t have decades of operating lore behind it. And if new diesels are successful they will all be FADEC so the pilot never had the chance to diddle with engine controls and won’t miss it.

But for the big majority of piston engines I now expect to die, or at least hang up my flying shoes, with mechanical fuel injection, magnetos and that supremely important mixture control still flying in most piston airplanes. My guess is that piston engine mixture and rpm operating techniques have passed into the realm of pilot religion, and all religions resist the new no matter what science may show. Just ask Copernicus.

Posted in Mac Clellan's Left Seat Blog | 35 Comments