AVwebFlash - Volume 21, Number 3b
January 19, 2014
Flying Platform Revival Under Way
A Florida company is hoping to revive a proven 1950s concept that mounted a ducted fan under a stand-up control station to create a 21st century version of the Hiller "flying platform." Flying Platform LLC, of Lake Placid, Fla., had the nuts and bolts of their design at U.S. Sport Aviation Expo in Sebring, Fla., and engineer Warren Novack said modern materials and engines have shaved half the weight off the Hiller design, which reached the point of U.S. Army trials in the 1950s. "We like to think this is an improved version," he said.
The prototype will be powered by two Rotax 503 engines for a total of about 100 horsepower turning counterrotating props. Novack said the ducted fan design is inherently stable and the physics prevent an upset. Directional control is by weigh shift and altitude is controlled by the throttle. "It's really easy to fly," he said. This aircraft has not flown but the company hopes to have it in the air by June. It will be offering kits that don't include engines at first. It's not clear where the company is aiming in terms of aircraft classification. The aircraft on display was about 280 pounds empty, which would put it in the Light Sport category. A reduction to 254 pounds, which Novack says is possible, would make it an ultralight.
Video: Flying Platform
In the 1950s there were various designs for flying platforms, but the technology wasn't quite good enough for a practical design. †Flying Platform, LLC displayed the beginnings of an updated version of the Hiller Flying Platform at the U.S. Sport Aviation Expo in Sebring, Florida and hope to have it flying by June. †After that, they'll be offering kits for sale.
FlareAssist Helps With Landings
An Alaska inventor has come up with a relatively low-cost ($2500) solution to a vexing problem for float and amphibian pilots and, well, really all pilots. John Pursey says his FlareAssist will help anyone skim (or grease) their landings through the use of ultrasonics. Pursey, whose background is in sensing technology, had one too many abrupt landings in his SeaRey amphib and put his knowledge to work. The result is a simple-to-install system with a transducer that sends ultrasonic measurements to a computer, which converts the impulses to annunciated distance calls in the pilot's headset. The device starts working at 15 feet and counts down to one foot.
Pursey said he designed the system for floatplane and amphibian pilots who encounter glassy water and have difficulty judging height in the last moments before touchdown. However, he said the system works as well on land and will be especially handy for taildragger pilots doing wheel landings. Beta versions of the system have been installed on several aircraft and Pursey will spend the next few months analyzing their results and tweaking the system before officially launching the product at Sun 'n Fun through Recreational Mobility and Jim Ratte as the exclusive sales agent.
Podcast: Every Landing a Smooth One?
Alaska inventor John Pursley had some jarring smooth water landings in his new amphib a few years ago and drew on his technical background to get some help. He spoke with AVweb's Russ Niles at the U.S. Light Sport Aviation Expo in Sebring, Fla.
Video: Skyleader 600 Makes U.S. Debut
Before the Soviet Union collapsed in 1991, the former Eastern Bloc countries supplied the Soviets with sophisticated aerospace products and services. †Now those industries have turned to civil aircraft manufacture. †One of those companies, Skyleader, showed off a new LSA at the U.S. Sport Aviation Expo in Sebring this week. †Here's a brief video report on the new Skyleader 600.
Southwest Pilots Were Visual To Wrong Airport
The NTSB says the pilots of a Southwest flight that landed at the wrong airport last week simply followed the wrong bright lights after opting for a visual approach to what they thought was Branson Airport in Missouri. According to the board's preliminary report, the crew was told by the Branson tower that they were 15 miles from the airport and cleared for a visual approach for Runway 14. The welcoming lights of Runway 12 at†M. Graham Clark Downtown Airport, in Hollister, Mo., about six miles north of Branson, caught their eye and they set up for an initially uneventful landing on the 3748-foot runway. "They confirmed that they utilized heavy braking to bring the aircraft to a stop and then advised the Branson Airport tower that they had landed at the wrong airport," the NTSB said in its initial report released Friday.
The captain of the flight had never been into Branson and the FO had only flown there once in daylight. Both are experienced Southwest pilots and told the NTSB the flight management system was properly programmed. As of Monday they were suspended but their final fate has not been released. There were 124 passengers aboard and Branson was an interim stop with Dallas as the final destination. Buses took the passengers and their bags to Branson where another Southwest plane arrived to pick up the Dallas-bound passengers a few hours later. The empty 737 took off from the other airport on Monday.
Senate Bill Joins House Action on Pilot Sleep Apnea Testing
AOPA is reporting that a group of senators has introduced a bill that would require the FAA to follow rulemaking procedures before it could adopt its much-maligned new standard for expensive sleep apnea testing for pilots. The Senate bill, introduced by members of the bipartisan General Aviation Caucus, Joe Manchin, D-W.Va., and Jim Inhofe, R-Okla., with co-sponsors Mike Johanns, R-Neb., and Mark Begich, D-Alaska, mirrors that of a recently introduced House bill that was voted upon favorably in committee and is positioned for a vote in the full house. Manchin said, ďItís just common sense to let the pilot community provide public feedback during the rulemaking process before the FAA finalizes any new guidelines."
Congressional action comes in response to the FAAís unilateral announcement of a policy that would require pilots with a body mass index (BMI) of 40 or greater to undergo intrusive sleep apnea testing, estimated to cost $3000. The FAA initially said it planned to lower the BMI requirement to 30 over time, potentially affecting more than 120,000 pilots. The reaction form the aviation community has been vociferous and overwhelmingly negative with demands from numerous organizations that the FAA withdraw the policy or submit it to the rulemaking process. The FAA has so far failed to identify any accident due to sleep apnea, but has relied on one airline event in which both pilots fell asleep during the en route phase, one due to sleep apnea. That event did not result in the FAA changing its policies on crew duty time.
The Savvy Aviator #56: Before You Yank That Jug ...
I last wrote about this subject about 18 months ago (Savvy Aviator #37), but it seems as if jugs are still coming off needlessly, so perhaps it's time to revisit the subject. Each week, I receive dozens of emails from aircraft owners seeking advice on maintenance. I really enjoy helping fellow aircraft owners, but I often get frustrated by some of the poor advice they get from their mechanics. Take this one, for example:
"Mike, I really enjoy reading your column. I'm having a problem and need some advice. My airplane is in for annual and for the second year in a row my TCM IO-520 engine has some low compressions. The compression test was done hot (or at least that's what I'm told). The IA is going to do another compression check today, cold, but I don't think that is going to change anything. "He said the leaks seem to be from the exhaust valves. I looked at the exhaust valve of the lowest-compression cylinder through a borescope, and the valve was red in color. The IA said that is because it's run too hot, and suggested that the culprit was my use of lean-of-peak mixture settings in cruise. "I fly about 100 hours a year. Most of my trips are about four hours long. I usually cruise between 8000 and 9000 feet. My power settings, at 8,000 feet, are about 22 inches at about 2400 RPM. I lean to peak on my JPI 700, then go about 15 degrees F lean of peak. My hottest CHT is never above 380 degrees F. What am I doing wrong when flying this airplane?"
I told this owner that he's getting flawed advice from his IA. For one thing, the owner isn't doing anything wrong. Fifteen degrees F lean of peak and CHTs below 380 degrees F are exactly where this normally-aspirated engine should be operated at 8000 to 9000 feet. He's doing a great job of powerplant management. For another, an exhaust valve is supposed to be red! The red color is from exhaust deposits on the face of the valve, and such deposits are perfectly normal. In fact, the cooler the valve is operating, the thicker the deposits and the more intensely red the valve appears. It's actually the absence of red deposits that tells us the valve is heat-damaged and leaking.
The key to whether or not the valve is burned is the appearance of those red deposits. On a normal valve, when viewed with the borescope (see photo at right), the red deposits have a relatively symmetrical appearance, with the redness most pronounced in the center of the valve face and less pronounced toward the edges of the valve face. That's because the valve face runs coolest at the center (where it's thickest and its heat is well-sinked by the valve stem), and hottest at the edges (where it's thinnest and not so well heat-sinked). The hotter the valve, the less red deposits there are; the cooler the valve, the more red deposits there are. In other words, red means cool and the absence of red means hot! (I know this sounds counterintuitive, because we're used to thinking of red and hot as being associated, but in this case it's non-red and hot that are associated!)
If the valve is leaking, there will be one (or sometimes two) hot-spots around the circumference of the valve face where almost all the red deposits are gone and you see gray metal. The red exhaust deposits will have an asymmetrical appearance (see photo at right), with the hot-spots identified as being where the valve is least red.
Don't Yank That Jug!
If the borescope inspection shows a valve with a normal-looking, symmetrical pattern of red deposits and no obvious hot spots, I would not authorize the mechanic to remove the cylinder. I would go fly it for a few hours and then repeat the compression test. (Preferably have another mechanic do the test.) To be on the safe side, I would continue to inspect the valve with a borescope every 50 hours (at each oil change). Since the aircraft has a digital engine monitor, I would also suggest keeping a close eye on the EGTs. Always place your engine monitor in its "normalize mode" when in cruise flight. This will level all the EGT bars at mid-scale and increase the sensitivity, so that small EGT variations become very obvious. If the exhaust valve is leaking in flight, you will see it on the engine monitor (provided it is in normalize mode). The classic signature of a leaking exhaust valve is a slow EGT oscillation of 30 degrees F to 60 degrees F that occurs about once or twice a minute (see graphic at right). Any time you see something like this, immediately borescope the cylinder and check the valve. In my experience, a burned valve becomes detectable under the borescope (via asymmetrical exhaust-deposits revealing a well-defined hot-spot or two) at least 100 hours before the valve actually reaches the point of failure. The engine monitor will also detect the problem, but with somewhat less lead time -- perhaps 10 to 25 hours before failure. Consequently, I believe that regular borescope inspections should be the first line of defense in detecting incipient exhaust-valve problems, with the engine monitor used as a backup. The use of regular boroscopy in piston-aircraft engine maintenance is relatively new, and many mechanics don't really understand what to look for. They almost certainly received no training on this in A&P school. Consequently, before authorizing a mechanic to pull a cylinder off your engine, you would be wise to do what this owner did: Seek a second opinion.
The same owner emailed me a follow-up question:
"Is there any regulation as to the minimum compression on a cylinder in order to pass an annual? My IA tells me the engine should not have passed the last annual because of low compressions."
Excellent question! Yes, there sure is. The applicable regulation -- 14 CFR Part 43 Appendix D (Scope and Detail of Annual and 100-Hour Inspections) -- states that an IA is required to perform a compression check at each annual and 100-hour inspection. It goes on to say that if "weak compression" is found, the IA must perform an internal cylinder inspection to ascertain the reason for the weak compression. The FARs do not define the term "weak compression." FAA Advisory Circular AC43.13-1B (Acceptable Methods, Techniques and Practices -- Aircraft Inspection and Repair) suggests that compression readings below 60/80 are considered "weak," but this default FAA guidance is superseded by any specific guidance offered by the engine manufacturer. Because both Lycoming and Continental (previously TCM) do offer specific guidance, AC43.13-1B is moot. Lycoming's guidance is that the inspecting mechanic should "consider" removing the cylinder if its compression is below 60/80, or if there is more than a 10-point spread between the highest and lowest cylinder. Lycoming also encourages (but does not require) mechanics to use borescope inspections to help assess cylinder condition. Lycoming's use of the word "consider" appears to give the IA some wiggle room, but most IAs will take the position that a Lycoming cylinder with compression below 60/80 has to come off. Continental's guidance is very different from Lycoming's. Continental's guidance appears in Service Bulletin SB03-3, which in my opinion is the best guidance ever written on the subject of determining cylinder condition. Every†Continental†owner should download a copy (by clicking on that link) and read it carefully. If you do that, you'll find that Continental says that the minimum acceptable compression reading is to be established using a "master-orifice tool" hooked up to the mechanic's compression test gauges. For most compression test gauges we've checked, the master-orifice tool sets the no-go limit between 41/80 and 43/80. However, each gauge is supposed to be calibrated with the tool prior to each compression test. (Nowadays, many compression test gauges come with the master-orifice tool built right in, so calibration is done simply by flipping a valve.) SB03-3 goes on to say that even if a cylinder indicates a compression reading lower than the no-go limit, the IA is supposed to inspect the cylinder with a borescope to determine the cause of the problem. If the borescope inspection fails to reveal a problem, then the cylinder should not be removed. Instead, the engine should be flown for at least 45 minutes (preferably a lot longer) and then the compression test repeated.
Have No Fear
Armed with my advice and a copy of Continental service bulletin SB03-3, the owner had a heart-to-heart conversation with his IA, and then reported back to me with the following:
"The IA just called and said that he has completed the annual, and agreed not to pull the cylinder. He said to fly the airplane for 25 hours and he will then recheck the compressions. I feel half afraid to fly the thing."
I advised the owner not to be scared to fly the airplane. Low compression never made anyone fall out of the sky. In fact, before issuing SB03-3, Continental actually ran some dynamometer tests in its test cell that showed an engine with all cylinders having 40/80 compression will make full-rated power. An engine with such low compression will also blow lots of oil out the breather and onto the belly of the aircraft, and will make what's left of the oil in the crankcase filthy in short order, but there will be little or no perceptible difference in performance, and certainly no safety-of-flight issues. An in-flight failure of an exhaust valve is no laughing matter. But as long as the exhaust valve looks normal under the borescope, you can be confident that it's not in imminent danger of failing. Regular borescope inspections, backed up by a digital engine monitor, will reliably detect exhaust-valve problems before they pose a safety hazard. I'm not suggesting that compression readings in the 40s are fine, nor that they should be ignored. Such low compressions are often associated with excessive blow-by that contaminates the oil with combustion byproducts and turns it acidic and corrosive -- not exactly the ideal environment for your expensive crankshaft and camshaft to live in. But such compressions will not cause any perceptible change in engine power or performance, and certainly won't make you fall out of the sky. So it's something to be concerned about, not something to be scared of. With such low compressions, it would certainly be prudent to re-check the compression and re-borescope the cylinder in 25 hours. If the compression continues to deteriorate or the borescope reveals the obvious visual signature of a burned valve or worn barrel, then the jug probably does need to come off for repair or replacement. In the meantime, however, the owner should have no qualms about continuing to fly the aircraft.†
RANS S-20: The Cub Archetype Done Better
One of my many character flaws is a complete disinterest in filling out forms of any kind including, Iím sorry to say, logbooks. I scribble down the legal requirements for currency, but thatís about it. As a result, Iím not quite sure when I last flew an airplane that wasnít an LSA. Might have been an Eclipse demo or perhaps Diamondís DA-40 diesel when I was in Austria last spring. Sadly, Iíll never be able to boast of the impressive number of types Iíve flown, but then if I donít care, why should anyone else?
Flying new LSAs is all but unavoidable because there are so many of them. Just at the Sport Aviation Expo over the weekend, there were three new ones and a couple of variants on existing designs. We try to fly as many as we can because readers and viewers are interested in these new designs. And frankly, I prefer flying simple little airplanes over squiring around a collection of aluminum or composite whose purpose seems to be moving a sophisticated avionics package and an iPad from A to B.
This has caused me to reset my thinking about light sport airplanes. Itís all but an article of faith that LSAs are overpriced and undervalued, a discussion weíve had in this forum ad nauseam.† Not wishing to have it again, I will say this about most of the light sport airplanes Iíve been flying: high priced or not, many are definitely better airplanes than what went before them. While some are reheats of traditional Cub-type designs, they simply fly and perform better. Whether that better is commensurate with the higher price is a buyer-beholder thing.
While at the Sport Expo show, I had a generous amount of flight time to compare RANS new S-20 Raven to my own J-3 Cub. RANS is a prolific designer of mostly experimental amateur-built airplanes, but theyíve got a fly away LSA model in the S-7LS and the S-20 will eventually be the same, although itís an EAB kit for now. The S-20 is a side-by-side taildragger with a 100-hp Rotax 912. So six decades after the J-3, why is the S-20 so much better?
Although itís about the same size as a Cubóitís actually a foot-and-half shorter with a five-foot less wingspanóitís vastly more commodious inside. With its tandem seating, the J-3 is tight and there is absolutely no convenient place to put stuff like a tablet or a kneeboard, while the S-20 has a large, easy-to-reach baggage compartment. And for a small airplane, the S-20 has so much cabin width that thereís no risk of shoulder rubbing.
As for the ergos and ventilation, the S-20 is quiet and warm compared to the J-3ís drafty and cold. Itís been 40 degrees here in Florida this week and those drafts that seep through the Cubís door and window chill the charm. Iím reptilian in my choice of temperature range. Iíd rather sweat than shiver.
As for handling, the difference between the two is stark. The old Cub has a ton of adverse yaw and while that makes it a good teacher for rudder use, itís not necessarily a desirable aerodynamic characteristic. The S-20 isnít quite feet on the floor, but it has little adverse yaw. One thing I donít like about many of the LSAs coming out of Europe is too-light control forcesóthis is definitely not desirable in any airplane. A couple of years ago, I slapped my fish scale on the stick of a Remos and found that the control forces were too light to measure and there was zero breakout force from a centered stick. The J-3 is quite heavy in roll and predictably, a little lighter in pitch. The S-20 splits the difference; itís light in roll, but thereís measureable force there. It feels like it ought to feel.
Just to show how the limitations of design ingrain habits, when I was taxiing the S-20, I was S-turning, this despite the fact that you can see almost as well over the nose as you can in a Cessna 150. While having the forward view blocked during taxi is part of the J-3ís old-world charm and accurately represents the pungent experience of 1930s flying, I wouldnít order that feature in a new airplane. Ditto for the brakes. Itís true that if youíre doing things right, you donít really need brakes in a taildragger, but thatís not the same as having BINOSóbrakes in name only. I donít mind being able to stop vigorously when necessary. Iím pretty sure I can avoid the noseover.
With 25 more horsepower than our Cub, the S-20 is a better climber and faster than the J-3. Part of that is due to lower drag. I notice this when flying any of the Cub-type LSAs. Despite being very current in the Cubólike 15-landings-a-week currentóIím always too fast and too high in the newer airplanes. By habit, I tend not to use the airspeed indicator as a reference, since I donít do that in the Cub. And that means until Iíve done a few landings, I tilt toward the fast and floaty instead of the slow and certain. Taildragger skills are only so transferable, at least for me.
This is especially noticeable in the pattern, where I like to fly a tight turn-in thatís perfect for the J-3, but will yield a too-high approach in something like the S-20 or the Legend Cubs. Since I seem to have trouble curing myself of that tight pattern, I do a lot of slipping to short final. Nothing wrong with that; itís a skill that needs to be kept alive.
As I mentioned in Fridayís blog, the arrival procedure into Sebring was a bit of a goat rope and rather than stooge around in circles over Lake Jackson, Randy Schlitter and I flew over to nearby Avon Park for some touch and goes, where we found a gusty crosswind up to about 15 knots. Iíll tackle that in the Cub, but the S-20 feels significantly more sure footed in such conditions, suggesting to me that the center of gravity is probably closer to the gear than it is in the Cub. When the S-20 plants, it doesnít have that Iím-about-to-break-loose-for-the-tulies feel that the Cub sometimes does.
Unforgiving ground handling will teach you the all-important lesson of staying on your game until the airplane is back in the hangar, but again, I wouldnít specify that in a new airplane. The Cub just happens to be that way.
In its fly-away LSA form, the S-20 will be in the mid $120,000s fully equipped, which is typical of what LSAs in the class cost. Iíve already explained in detail why I think these prices are about what they should be, given the cost of building new airplanes in a market that canít sustain volume. If you want to rage about how outrageous that price is, be my guest. But by now, itís a lost cause, Iím afraid.
For a third as much, you can find a nice, restored Cub that will be a terrific fun flyer. But in the end, the S-20 is just a faster, more comfortable and more sophisticated airplane. Itís not just incrementally better, itís a lot better. And seriously, if 75 years of progress didnít make it so, it would be scandalous indeed.†
Click here for a video report on the RANS S-20.
Photo Gallery: Sebring Draws Weekend Crowds
Photo Gallery: Sunny But Cool at Sebring
Video: World Aircraft Starts Up in Tennessee
World Aircraft is starting production of two light sport aircraft at its base in Paris, Tennessee. †The company exhibited at U.S. Sport Aviation Expo in Sebring, Florida.
Video: RANS' New S-20 Raven Debuts at Sport Expo
RANS Designs is out with a model called the S-20 Raven, an evolution of its popular Coyote series. †At the U.S. Sport Aviation Expo in Sebring on Thursday, AVweb's Paul Bertorelli took the Raven for a demo flight, and here's his report on the airplane.