Veloce 600, 6 seat pressurized twin auto-converted engines.

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mm4440

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Jan 14, 2012
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LA area, CA
It is simple, most of the time you will get away with it, all of the parameters necessary to cause a problem will not develop. However when the Gods unite against you what are you going to do about it? Crash and live the rest of your life in a wheel chair drooling into a cup? Or have a better plan?
If you have an engine go out at 35k you have some time to descend and restart.
 

mm4440

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Great post. Thanks.

Its important to note that the fuel is actually boiling (not really evaporating) however the effect is the same as you say, ie the fuel cools by giving up its enthalpy of vaporization and stays liquid. And also, yes, the lightest molecular weights (eg isopentane) boil off first. Its important to note the change in Octane of the fuel when the lighter fractions are lost.

As we climb, to altitude the lighter fractions boil/evaporate and the fuel loses its octane the higher you go. The irony, of course, is that engines rely on higher octane to avoid detonation, vapor lock etc. but as we climb, the fuel is losing the very octane needed to fly high. I guess this fact hurt the B29's trying to get to Japan hence all the fuel research at that time. The 'fix' was to fly lower which I always thought was to improve bombing accuracy, but maybe it was the fuel as well.

Its also worth noting how much fuel can be lost through boiling/evaporation. Up to 20% in the charts up to 50,000 examined in the old NACA E5H27 report.

I guess some of this discussion is finding its mark as Veloce 600 Specs now lists 25,000 as the cruise ceiling. A lot less to worry about at 5.45 PSIA.
Lower altitudes reduced fighting the jet stream headwinds too.
 

PMD

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Apr 11, 2015
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659
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Martensville SK
I have to comment that their digital airplane looks almost like what I imagine a great real airplane could and should. Difference is the reduction in cross section should not take place until further back. AND, of course, the engines would positively HAVE to be diesels - for so many reasons.
 

rv6ejguy

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Calgary, Alberta, Canada
It's a good looking airplane but AM builds SI engine packages so it doesn't make sense for them to install diesels. Restart on a turbo diesel at 35,000 feet would also be challenging...
 

PMD

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Apr 11, 2015
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Martensville SK
It's a good looking airplane but AM builds SI engine packages so it doesn't make sense for them to install diesels. Restart on a turbo diesel at 35,000 feet would also be challenging...
If you remember that the Germans had virtually unlimited and absolutely unchallenged intelligence gathering before the Battle of Britain. This is because Junkers diesels were flying at altitudes well beyond ANYTHING else. It took the Brits many months to build (IIRC compound supercharged) one-off Spits to reach their altitude, thus ending the overflights and giving the observation advantage back to UK radar. I doubt their old jerk pumps would re-start at those altitudes, but from a temperature related perspective diesels are started all day (and night) long in the Arctic with little fuss. HPCR made that happen much better than IDI or even DI at lower injection pressures. The air side of re-start is quite do-able.
 

rv6ejguy

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I doubt their old jerk pumps would re-start at those altitudes, but from a temperature related perspective diesels are started all day (and night) long in the Arctic with little fuss. HPCR made that happen much better than IDI or even DI at lower injection pressures. The air side of re-start is quite do-able.
Atmospheric pressure at FL350 is 3.5 psi so your effective CR is 0.23 of SL. Ambient temp is -65F. A challenging environment to restart a diesel. If the turbos die, you have an immediate flame out. These reasons plus trying to warm the fuel and the cabin at the same time and higher weight makes the diesel a poor choice for flight up there.
 

zolotiyeruki

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Joined
Apr 13, 2021
Messages
8
Is the Aeromentum Psru used:
1. Planetary as is used in turboprops and turbine helicopters?
2. Set up for oil controlled CS props?
3. Have a track record over 1000 hours without failure?
As I understand it:
1) No, because they use inline engines, and need to get the prop high enough (and there are other issues with planetary gears)
2) No, but there are a few electric in-flight adjustable props available
3) Of the AM15 line, their longest-life engine so far is 4,000 hours, I believe. I think I heard them say somewhere that they have over 100 flying engines out there now, plus 75 in airboat fleets. The 260HP 2.0L engine is new, so it hasn't built up a history yet.
 

rhbelter

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Mar 9, 2015
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Location
Carmel CA
Great post. Thanks.

Its important to note that the fuel is actually boiling (not really evaporating) however the effect is the same as you say, ie the fuel cools by giving up its enthalpy of vaporization and stays liquid. And also, yes, the lightest molecular weights (eg isopentane) boil off first. Its important to note the change in Octane of the fuel when the lighter fractions are lost.

As we climb, to altitude the lighter fractions boil/evaporate and the fuel loses its octane the higher you go. The irony, of course, is that engines rely on higher octane to avoid detonation, vapor lock etc. but as we climb, the fuel is losing the very octane needed to fly high. I guess this fact hurt the B29's trying to get to Japan hence all the fuel research at that time. The 'fix' was to fly lower which I always thought was to improve bombing accuracy, but maybe it was the fuel as well.

Its also worth noting how much fuel can be lost through boiling/evaporation. Up to 20% in the charts up to 50,000 examined in the old NACA E5H27 report.

I guess some of this discussion is finding its mark as Veloce 600 Specs now lists 25,000 as the cruise ceiling. A lot less to worry about at 5.45 PSIA.
Ahoy, all,

MANY years ago (in the 50's) I flew AJ Savages (see wiki), the U.S. Navy's first built Nuc Attack plane. It looked like a twin, but harbored a jet (J-33) in the aft fuselage, and carried a big turbocharger in each nacelle, so pilot work-load wise, you were running FIVE engines. We routinely flew at 45,000 feet, and the airplane would go to more than 50,000'. The airplane carried (the first???) engine analyzer, which the navigator would keep an eye on, because the power setting that we flew at would see a jug blown if one plug in a cylinder went dead. The R2800 engines in THIS airplane were 250 hour engines!!! They seldom got there. Didn't quite, just wore out, and blew oil. A big boxy looking airplane, to carry the 'fat-man' nuc. It would, flat-out, do more than 450 knots true, and the jets back then were only good for a little more. Nice handling, very nice carrier approach, but easy to 'break'. (I never did). Never any fuel problems, (115/145 performance number) and it had a very high rate of climb.

Enjoy /s/ Bob Belter
 

Urquiola

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Aug 23, 2013
Messages
251
Location
Madrid, Spain
The Attached document is an old Spanish utility model, a counter-current heat exchanger, heating fuel with engine cooling fluid.
I ignore if 'vapor lock' will come, but this may help solve the build1633785750685_Economizador 0248478_U Manuel Fdez Fdez.jpgup of ice in carb, from fuel change of State into vapor absorbing heat.
The concept was installed in the Jet Trainer 'Iskra', 'Spark'.
Blessings +
 
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