I read about the Celera when it was posted to the GA omnibus thread:
I see hoax (or at least ridiculous levels of wishful thinking) written all over that thing. I’m now old enough that I could be proven wrong as a lot of geezers eventually are. But the progress they’re talking about having in the bag is far and away beyond what much better-funded R&D operations have failed at and are failing at.
Depends on the plane.
From a maintenance standpoint the single is much cheaper to maintain. From a flying perspective it’s much safer in a landing pattern. It’s only when a twin engine plane reaches cruise altitude that it’s safety advantage kicks in.
The easiest apples to apples comparison is a plane developed as both a single and a twin. A stock twin Comanche has a cruise speed of 169 knots using (2) 160 hp engines. The high performance single engine Comanche with a 400 hp engine has a cruise speed of 185 knots. There’s an aftermarket version of the twin with (2) 200 hp engines and the specs are similar to the 400 hp single. So no performance gain but a much higher maintenance cost for the twin.
Looking at costs a twin engine plane has 2 constant-speed props to maintain. 2 electrical systems to maintain. 2 fuel distribution systems to maintain. A twin engine plane requires a fueled heater in place of free engine heat from a single. .All of these have 2 sets of wires and cables controlling them.
What you get with a twin is higher purchase price, higher maintenance costs, and less safety at takeoff/landing. What offsets this is a spare engine that gets you to an airport in an emergency once you’ve reached altitude.
I was once in a twin engine plane that lost an engine at takeoff rotation and the person flying it was a 25,000 hr pilot. It was all he could do to keep control of the plane. It dragged the plane sideways off the center line and he couldn’t get it back on the runway. Fortunately he had juuuust enough power to climb over an obstacle that he couldn’t steer around.
It seems some twin piston planes can climb with only one engine. The DA-62 claims you can climb to 13,000 feet on one engine (although they do not say how it is loaded to do that).
Granted it is a pretty expensive and modern plane designed for safety so they very much were working towards a cost is no object plane that most other light twins won’t manage. But it does show it can be done.
I’ve seen a crap-ton of “revolutionary” thinking and even prototypes in my time as a pilot, but very little actual progress. Re-post when they have a production line and are actually selling aircraft.
I’ve flown a single-engine smaller Diamond aircraft (DA20 Katana) - the airframes are derived from motogliders and have superior glide ratios (between 11:1 and 14:1, in contrast to the typical 7:1 to 9:1 for Cessna and Piper single-engine fixed gear fixed props) for the small end of GA. They make a lot of use of plastic and carbon fiber in Diamonds. Between the relatively light weight and aerodynamic efficiency yes, I can believe their claims. Notable, however, is that Diamonds make use of 1990’s technology, not 1950-1960.
I’ve flown airplanes as old as 1942 (Stearman PT17) and as young as 2005 (Ikarus C42, also 1990’s technology even if the one I flew rolled off the assembly line in the 00’s). A decade or two of aviation advances make a large difference in handling, performance, efficiency, and safety. Those are both single-engine two-seaters, but the younger of those two is 1/4 the weight, can carry more, burns 1/4 of the fuel per unit of time, has much more docile stall characteristics, and is a hell of a lot easier to handle on the ground and also easier to handle in the air. Don’t get me wrong, I really enjoyed my time in a biplane, but if you handed me $100k and said buy a plane I’m pretty sure I’d buy one younger than myself, not older. The younger the better, as a general rule.
Here’s the DA-62 pilot manual straight from the factory website.
The engine failure during takeoff procedure says in so many words that climbout may not be possible under heavy/hot/high conditions and if so cut power and aim to land on something soft. Even a go-around with the bad engine already feathered may not be successful if started below 800 feet above the ground.
The performance data says the airplane cannot make the legal definition of a safe climb gradient even starting from sea level at max gross weight. You need to have 3 empty seats or 50 gallons of air in the fuel tanks to make a sea level take off and fly out of having an engine failure. And even then that’s on a cool day and it’s a real skoshy manuever; better be on your toes!
The Diamond is not magic. The thing that’s not obvious to a layman is the tremendous difference between you’re cruising along at e.g. 5,000 feet at cruise speed with gear and flaps up then an engine fails versus you’ve just lifted off and the same failure occurs with the gear down, the flaps partly extended and the airspeed much lower. Climbing out of that latter hole is the hard part. If you live long enough to get the gear up, the flaps up, and the speed up above best single engine climb speed, then yes, you might be able to slowly inch your way up to 5,000 10,000 or even 13,000 feet before it runs out of climb capability & fuel.
All the hard (and frequently impossible) part was back near the runway.
Here are some Diamond DA-62s for sale. They ballpark for $1.5M. Nice toys for some fortunate somebodies. It’s the Maserati of light twins. Here’s some aging Chevy’s.
Slight, but hopefully interesting hijack:
When we bought our first airplane, we discovered it had been flown from the west coast to Hawaii in its early life. There were numerous entries in the maintenance logbooks about removing seats and installing fuel tanks in the cabin. Then the next entries were from an FBO in Hawaii, and continued for 2-3 years there. Following that, a bunch of entries about demating the wings and engine for shipping, and the next set were re-assembling the plane in San Diego.
I always wondered if the original owner flew it to Hawaii and decided he didn’t want to do that again (and shipped it back). I would love to know that whole story.
My mom worked at Gibbs Flying Service at MYF for about 20 years.
Do any GA twins (or any GA plane really) support the equivalent of a War Emergency Power setting? The remaining engine might require a complete rebuild after landing, but an extra 10-20% of power might mean the difference between a successful and an unsuccessful go-around (I’m not suggesting anything crazy like methanol injection, just exceeding the normal RPM limits and such).
A pilot can certainly red-line the engine(s), exceed recommended airspeeds, and so forth but anyone who does is venturing into unexplored territory and risks Something Awful occurring prior to meeting their planned destination.
I have seen airplanes that successfully landed despite literally bent airframes, and on one occasion an aerobatic airplane that managed to land with a main spar broken clean through (which gave me a lot more respect for the Dacron skin which was literally the only thing holding the wing together until it reached the ground.
Needless to say none of the above is recommended.
I’ve also seen airframes that can only be described as smashed after less successful incidents when engineered parameters were exceeded. The occupants faired even worse.
when you’re taking off with a standard general aviation piston plane you’re using everything the engine can produce. There’s no secret power setting you can switch to. At cruise altitude the limitation is the air frame. If you add more power you’re still limited to the air speeds set by the factory.
WWII aircraft engines were a different story. engines were often mechanically de-rated at the throttle but that could be by-passed in an emergency or as you suggest an auxiliary fuel source was added.
Commercial jet engines are a similar. You can add more power in an emergency and it will reduce the life span of the engine and that’s a function of increased engine temps. Airline pilots can better explain the penalty.
But you can take the SR-71 as an example. When it was being used as a piggyback test bed for NASA they increased the thrust of the J-58 engines by 5% using an uptrim temp increase of 75 deg F. The TBO time of the engine went from 400 hrs to 50.
As @Magiver said. Normally aspirated piston engines are putting out 100% of what they possible can on every takeoff; there’s nowhere to find more power.
So called “war emergency power” was related to supercharged engines. For normal ops the Boss decreed you only laid on so much boost; any more and you’d wear the engine out too quickly. But as between a sure-thing crash or shoot-down and needing an engine overhaul, better to over-boost the engine & maybe live. And if the engine did come unglued right then, well, you were about to crash & lose the airplane & pilot anyhow. No downside there either; at worst the Air Corps breaks even and maybe they come out ahead. As to the pilot … Well sometimes it sucks to be you.
Nowadays superchargers are rare on GA aircraft piston engines, but turbochargers are common on the higher-powered engines. Largely as a way of delivering sea-level power output at higher altitude. Essentially they’re designed to ram enough air into the engine at, e.g. 10,000 feet that the engine thinks it’s still breathing sea level air and hence puts out sea level horsepower. There’s no way to “turbocharge” the props or the wings, so the overall aircraft performance still degrades with altitude, just not as severely.
Most of these turbocharged engines when operated down near sea level can be throttled up to the point that the turbocharger is stuffing well over sea level pressure into the engine. Standard sea level atmospheric pressure is just shy of 30" of mercury. 35" or even 38" might be typical takeoff power for a modern big turbocharged piston. And typically the throttles are mechanically rigged so the pilot could put more boost in before hitting the mechanical stops. But the pilot isn’t supposed to. The incremental slack space at the top of the throttle range is just enough to compensate for high or hot or whatever. So maybe at sea level you could stuff 42" into an engine rated for 38" max. How long will it last at that boost? You’re the test pilot, you tell us. Maybe 30 seconds, maybe 30 minutes, maybe 30 hours.
As to Jets …
Pre-electronic jet engines were the same way. Pushing the throttle to the mechanical stop may overpressurize the engine, exceed the max RPM on one of the various rotor spools, or overtemp the combustion & turbine areas. Exceeding any of those several limits is real bad for longevity. But could be tried if the alternative was ground impact.
The McD-D MD-95 AKA the Boeing 717 had/has fully electronic engines, the BR-715. It included an emergency extra power setting like WEP. There was a soft detent on the throttle travel that was the normal max. Push the throttles to there and the electronics set normal max output, mindful of all the limits. But you could push through that detent and get another ~1" of throttle travel that told the electronics: “Unless you too want to be smashed on the rocks, flog the horses harder; let the temps and RPMs go up a bunch more.” It was good for an extra 10 or 15% thrust, but there’s no assurance the engine would hold together more than a few minutes and may well need need a full multimillion dollar overhaul even if it does hold together. Our procedures were to use it for windshear escape and ground proximity alert escape. Otherwise it was verboten.
Twin Piston Take-Off Performance
Most of my piston twin time is in a Shrike Commander and an Islander.
The Shrike was certified in Australia with two max take-off weights (MTOW), the lower weight was for IFR and ensured you could maintain a positive climb in the cruise at 5000’ in the standard atmosphere while the higher weight was for VFR and came with no performance requirements.
If you had an engine failure at the lower IFR weight and the wheels and flaps were up and you had sufficient airspeed and the engines were delivering their nominal power and the airframe wasn’t too bent AND it’s the standard atmosphere (15°C and 1013.2 hPa at sea level) then you should be able to climb to 5000’
So if you are taking off in the Shrike (or most other piston twins) and suffer an engine failure, there are no guarantees. You control the aircraft, clean it up (gear up, flap up), feather the failed engine, and assess performance. If it’s climbing then you fly your terrain escape plan, if it’s not climbing then you land (controlled crash) straight ahead.
IIRC the TBM-940’s engine is flat rated to 850 HP but it supposedly can produce 1550 HP.
I do not know if a pilot can “redline” the engine or not to get at that extra power.
(My limited understanding is a flat-rated engine will give you 850 HP in any conditions…the engine is limited but will give you a consistent oomph regardless of conditions…I may be very wrong about that.)
Only using that as an example. I realize there are huge differences between various planes.
You understand flat-rated correctly. There’s no such thing as a turbocharger for a gas turbine. Or said another way, a turbocharger is a gas turbine is a turbocharger.
In an ICE engine the turbo can shove extra air in there which has the effect of providing constant max HP from sea level up until the air in thin enough that full turbo boost just barely raises the cylinder air pressure to sea-level equivalent.
In the gas turbine the same effect obtains. As you go higher the thinner atmosphere processed by the compressor delivers less and less pressure to the combustor. Once you get high enough that max RPMs are only able to deliver some arbitrary level of power you’re done. Typically they decide the max flight altitude (“service ceiling”) of the aircraft, see what power output that requires, then declare that to be the engine’s “flat-rated” max. At all lower altitudes either the electronics or the pilot manages the thrust to produce not more than that much horsepower / torque / whatever.
To an even greater extent than pistons, longevity in gas turbines is related to temperatures & RPMs to some exponent greater than 1. Made up example:
longevity = 1/(temp^2)
Part of the reason so many turboprops are bulletproof is that in most installations they don’t run the temps anywhere near levels that eat into longevity. The same basic engine installed in an airplane that needs more power may differ only in software that lets it run hotter; it may have no mechanical differences. And it will last a correspondingly shorter time before needing inspection and/or overhaul.
This longevity vs temp thing is also used in airline ops. We rarely use full power for takeoff. Instead we figure out the minimum power needed to safely lift today’s load off today’s runway with today’s weather. Then use only that minimum necessary. A similar sliding reduction is also used for the climb towards altitude. The reduction typically washes out somewhere between 10 & 20K feet. Above which we’re running at the full rated long-term power for the rest of the climb.
Is 4 prop engines and an auto-eject system with an emergency reserve chute an option?
Seems like a lot of notable people have been killed in small, private plane crashes.
The Cirrus Aircraft Parachute System (CAPS) has been around for 20 years and is a parachute for their small planes. It’s effectiveness is debatable but overall seems better to have one than not.
There have been ballistic recovery parachutes for small airplanes well before Cirrus. Some can be retrofitted to older models.
They’re fine, and they do save lives - but they say right on the canister that they are no guarantee of survival. People do not understand either their purpose or their limitations.
The Robinson R-22 Beta (see avatar 
) has a Lycoming O-360 engine of 160 h.p.; but it’s derated by putting a red line on the manifold pressure gauge to 131 continuous h.p. You may run the engine at 142 h.p. for up to five minutes for takeoff. See page 2-10 of the POH.
that was the going philosophy that killed a bunch of people trying to cross the Atlantic. It seems logical but as more engines were used the bigger the plane got. The bigger the plane the more fuel it required and the heavier it got. The end result was a higher likelihood of “something” failing.
I say this to explain why Lindbergh succeeded. He understood that less parts meant fewer failures and it allowed him to focus on making a simple design more reliable.
the reason we went to jet engines is because they are much more reliable than piston engines. And as power increased we were able to reduce the number of engines from 4 to 2 while increasing the size of aircraft.