Top Letters And Comments, August 31, 2018

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Image: Ramon F Velasquez - CC BY-SA 3.0

Image: Ramon F Velasquez - CC BY-SA 3.0

Swift Fuels Suspends PAFI Activities

 I'm not at all surprised to see Swift bow out. They began life as a biotechnology company shopping microbial technology that might be used to produce aviation fuel. The economics were rarely discussed. During the clean energy boom eight years ago they (and other marginal concepts) were able to find financing and government grants. When that ended, Swift reinvented itself as a petrochemical company and got itself selected by the FAA - an agency that is not known for, and shouldn't be expected to possess, chemical engineering expertise. I'd like to make a couple of comments about mixing these candidate fuels. If you don't like chemistry, stop reading and I won't be offended. Each fuel has a fairly unique set of chemical components and, when mixed, the properties (vapor pressure, relative volatility, tolerance for water, detonation resistance.....) of the resulting solution can be very different from either starting fuel. Furthermore, these do not change in linear proportion as the fuels are mixed. Mapping these effects It is a daunting problem and an area of considerable research in chemical thermodynamics. I think we are underestimating the difficulty of certifying multiple fuels in all combinations. It is entirely possible that the STC process will be more effective when it is directed toward modifying existing power plants to tolerate current unleaded fuels. The market will sort it out.

Kim Hunter

If you look at back issues of flying and other aviation magazines you find this debate about unleaded avgas has been going on for decades, since the 80's at least. I have a 2014 dodge. It can run on anything from 87 to 93 octane with no problem and adjusts the timing to prevent preignition. We are looking at this from the wrong end. If you want unleaded fuel you need to update the engines and ignition systems. We are still using systems designed in the 1950s. The FAA needs to certify drop in electronic ignition systems for current engines which, with variable timing, would allow the engines to operate on a variety of octane levels with minimal performance loss and reduce engine problems such as stuck valves and other issues due to lead. Our problem isn't so much the antiquated rules of the FAA regarding fuels but the antiquated rules requiring us to use ancient technology when so much more is available.

Rodney Hall

The Swift fuel 94 Octane lead-free is a great fuel. Luckily we have it at the Sebring Florida airport. Everybody that uses it reports the engine runs way better with it. Which kinda makes sense, lead does not burn, so whatever quanta it occupies in the fuel it is dead weight. Swift fuel or any comparable fuel burns 100% so per weight basis the pilot gets more bang for the buck. I run it in my old GMC Yukon and I can tell the difference. Anyone that has an 80/87 fuel capable engine and has access to Swift fuel ought to try it for themselves. I am eagerly awaiting the day I can fill up with 100 Octane Swift in my Beech Sierra, or comparable fuel that has no lead. Lead is poison to the engine, I'd like to see it go away.

Max Mason

Anyone who reads John Deakin (AKA "Pelican's Perch") would know that the PAFI process was pretty well doomed from the start. Deakin opines that a drop in 100 UL is unlikely, given the other restrictions from OSHA and EPA on toxicity of available high-octane hydrocarbons. You can either have octane or low toxicity, but you can't have both. What I find amazing is that the FAA apparently has no one who understands (or cares) about how developmental studies are conducted. To enter into a process to "refine" the formulation of a fuel and not allow any changes to the original mixture is unthinkable. A freshman chemistry student knows better than that. For once, however, the little guys get a break on this mess. Older low octane engines can do just fine on either ethanol free mogas or the (approximately) 94 octane avgas that is left after the lead is removed from 100LL. The big-bore high HP engines will have to have modifications to accept the same. But, their owners are better able to afford the costs than the unwashed masses. The alternative is to hope that GAMI or another STC applicant can come up with a universal substitute that may have its own problems, especially if the compatibility with other fuels cannot be overcome. Oh, and with all due respect to those who worship the kerosene gods, diesel engines are probably not the answer. While they may work in new airframes, they are hideously expensive, complex and not field repairable. Squeezing them into the legacy fleet is not an option and the whole idea of a replacement fuel is to keep the legacy fleet flying. Electronic ignition with variable timing is a much better, and more cost effective solution. Plus, it actually gives some return on investment through better fuel economy, longer plug life and lower maintenance costs. As usual, the free market can probably develop an answer if the FAA will just get out of the way.

John McNamee

Electrics and Diesels

On July 26, Paul commented in "Electrics are Meh" that the near-term future seems to lie with hybrids, but that it is more efficient to have the gasoline engine drive the propeller directly without the weight of the batteries, speed controls, electric motors, etc.

The next day, Paul said in "The Diesel Dance" that they "will have a steep uphill slog."

I think the only hope for diesels is as a part of a hybrid electric powertrain. Because diesel engines today produce a very sharp impulse to the shaft and prop every time there is a combustion event, diesel engines need to have heavy fly-wheels, gearboxes, torsional dampers, and robust propellers.

In a diesel-electric power train, the diesel would drive a generator directly, and there would be no need for the heavy fly-wheels, gearboxes, and torsional dampers. The propeller could be substantially lighter because the smooth torque applied by the electric motor would reduce the stresses on it.

Electric motors are relatively light, and the batteries in a diesel-electric would need only enough capacity to act as a reserve for a return-to-land engine failure on takeoff emergency.

A diesel-electric hybrid may, or may not, be as efficient as today's gasoline engines, but if a non-avgas fuel was required, the diesel-electric hybrid may be a more suitable alternative to a straight diesel.

Andrew Probert

When There's No Need For Speed

Having taught "bush" flying, I consider your comments on the value of appropriate speed to be right on. That applies to every airplane I have flown from 600 lbs. to 48,000 lbs.

Having just flown an Avid Flyer that was not quite rigged properly, I agree on the idea that very light aircraft can be a handful. (Also, the Avid has ATROCIOUS adverse aileron yaw.)

Ian Hollingsworth

I agree that a pilot must select the exact proper speed under local conditions for safe landings. However, I feel the location and type of speed indicator - whether steam or tape - is not the appropriate instrument for the task.

For steam style the location is too low in the cluster or with a tape it is part of a confusing array.

The pilot cannot see "trends" in speed variation well with either of these speedos - just sudden information of a change - and 5 Knots could be the difference between life and death.

My suggestion is to locate the speedo on top of the dash panel where the pilot could see it while looking thru the wind screen. This would be a digital style and the pilot could easily monitor TRENDS in airspeed and adjust (not correct) in small increments of throttle and pitch.

I think this would be easy to test as very fine recording of elevation are to be had with Flight Monitoring Apps. A more expansive test could be done with pressure sensors on the yoke and RPM recordings from the engine. My feelings are we would see much less yoke pressure and fewer and smaller engine RPM changes on final.

Frank Kalinski

You nailed this one. My Mooney days taught me that 5 Knots too fast made for long and bad landings. More than one Mooney pilot has pushed his nosewheel to the ground first resulting in damage to important things like props and engines. I flew with a Mooney test pilot in Kerrville when they were testing an aerobatic version of the short body Mooneys. When I came in for a landing a couple of knots too fast, his hand reached slowly towards the yoke to prevent me from "pushing". "Don't worry", I said, "I know I just have to wait for it to slow down".

Landing speed is like porridge, too hot is no good, too cold is no good, but just right is...a good landing.

Carl Marbach

The one thing I took away from your LSA video was exactly what you said ... too much speed is an issue. After many decades of flying my C172 with zero issues, I came close to crunching it on a blustery day last year (coming back from an ADS-B Rebate flight, BTW). I couldn't hold the centerline and was headed off the runway into the cross wind when I decided to get outta Dodge. I then ended a subsequent approach to a grass runway when I decided that wet grass would be worse. I shoulda gone around to line up with a "backup" runway locals use -- a taxiway -- but didn't. I then found out how good my brakes work. Subsequent self analysis yielded that I was too fast on the first landing and forced the successful one because I got nervous. Watching your video solidified my own thoughts and I learned from your analysis. Thanks. We're taught to fear stalls so much that we go too far the other way, I think. During my FR two years ago, the CFI complimented me on holding heading during a pretty deep stall sequence. I think that practicing slow flight and being confident on recognize what 'your' airplane does -- as you say -- is far more important than adding speed because you fear stalling. But NOW ... I have a new tool. Talk to myself and then answer. Why didn't I think of that? :-)

Larry Stencel

The critical difference between a traditional round, moving-hand display, and a "sexy" moving-tape display is this: the tape display has to be READ; then the acquired information has to be processed - the dial display information can be swallowed whole. Example: You've likely seen one of those large-form-factor clocks - the ones where the hands are visible; mechanism that drives them is buried in the wall; and the presentation may or may not include wall-mounted numerals or place-marker chits. Even without the chits, most people can glance at the display and tell the time within three minutes or so. Even when the display includes only an hour hand (no minutes pointer), most folks can gauge (couldn't resist the pun) the time within ten minutes or so. At a glance. No pondering required. Neatly, the angular presentation also offers a way to add and subtract blocks of minutes - or hours - VISUALLY: 90 degrees = 15 minutes or 3 hours, etc. It's a marvelous piece of human-factors engineering. Really. A ROTATIONAL sweeping-needle display leverages humans' amazing ability (adaptation?) to see and interpret ANGULAR-presentation information, including direction-and-rate-of-change - right to the point of being able to fly accurate phugoid trajectories based solely on the ASI display. By contrast, in Paul's own words, "the airspeed tape is like a berserk slot machine." Not to mention (but I'm about to) the running argument over whether the tape displays should show higher airspeeds descending from above, or rising from below... Cool is tempting, but effective is good. I say this less as a pilot, than as someone who has spent a LOT of time designing man-machine interfaces. As a side point, I'm STILL waiting for somebody to do what seems obvious to me: integrate AoA information into an ASI display, WHERE IT BELONGS. Just put colored AoA arcs (or pointers) onto an OLED "dial" face; expand/contract and rotate the arcs in response to changes in AoA - by reference to the MOVING airspeed needle. After ten minutes of practice, you could maneuver through the full range of airspeeds at a constant angle-of-attack - by loading and unloading the wing with the elevator. What a teaching tool THAT would be! Lecture/rant over.

Tom Yarsley

Garmin/uAvionix Lawsuit

I'm puzzled by Jim Holdeman's comment on the lawsuit. He refers to 2.4 GHz spread spectrum comm technology, but that's used in cellphones and is based on the Markey-Antheil patent #2292387 of 1942 of frequency hopping ("Markey" is Hedy Lamarr, and is the name of her husband of the time of filing). But spread spectrum is NOT ADS-B 1090 MHz/978 MHz frequency and could NOT be used with 2.4 GHz cellphone frequencies. The frequency hopping would prevent air-to-air communications of ADS-B OUT data between aircraft, so would be impractical. If Beard wants to change ADS-B to 2.4 GHz, convince the FAA to make the change, but that ship has sailed and I'm not going to re-equip for a new frequency on someone else's whim.

The lawsuit between Avionix & Garmin has to do with the '301' patent filed first by Garmin that patents the extraction of the existing ship's squawk code and other encoded data from the outgoing transponder signal using a 'receiver' built into the ADS-B box. Because Avionix uses this technique, albeit with a clever 'receiver' on the DC power bus collecting conducted EMI flowing back onto the DC bus from the transponder, it is, nonetheless, a 'receiver' and can be construed as violating the patent, just as anyone trying to patent spread spectrum technology nowadays can't do so because of the Markey-Antheil patent of 1942. (the 1942 patent is long expired, so folks can use the tech, but they can't claim patent rights on anyone else.) Garmin's patent was granted in 2011, so it's still valid.

David Rosing

Why Light Sport Airplanes Suffer So Many Crashes

Thank you so much for "Why Light Sport Aircraft Suffer So Many Crashes". Your presentation confirms my suspicions generated while flying in Africa for a conservation organization. LSAs were seen as an inexpensive way to get aerial surveillance into national parks. I flew a Cessna 206 and was skeptical about LSA use for the reasons you give in your presentation and more. When the director of the national park in Congo where I was working crashed and destroyed the park's LSA I began to grumble given not only that crash but three other LSA crashes in other national parks. I recommended Super Cub or Husky replacements but that fell on deaf ears because that would mean the pilots would have to get a private pilot license. Actually, all should have commercial licenses because the pilots were receiving compensation but that fell on even deafer ears. The 5th crash occurred and killed the just newly minted LSA pilot in a new Zenair with an illegal bladder tank on the shelf behind the pilot. He and his passenger burned to death in the Zenair, 90 kg over gross weight in windy down drafty conditions. Even then, I unable to get traction on aviation safety and management and did not renew my contract.

John Sidle

Colorado Now Has A Spaceport

This is one of the dumbest articles you've published. Considering the volume of information in my inbox, your help with winnowing the "fluff" out of your publication would be greatly appreciated.

John Gebhard

Space Force

The reason for implementing space force is to keep China and Russa in check, therefore it is long overdue. NASA really, they could not even keep our astronauts safe.

Allen Churchwell

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