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Not entirely true. Where fitted they are generally available for use in the air in an emergency if required. Also for some longer ETOPS certifications it is a requirement that they are capable of being run in the air in case of engine shutdowns.The list of aircraft with APUs is massive... And let's be clear, APUs are not a means of propulsion. They are there to generate power for auxiliary systems on the ground. Not many APUs can be/were used in the air. The majority of modern airliners have APUs that only work on the ground when the main engines are not generating AC power.
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Not entirely true. Where fitted they are generally available for use in the air in an emergency if required. Also for some longer ETOPS certifications it is a requirement that they are capable of being run in the air in case of engine shutdowns.
lawed - but one of my French favourites - The Mighty Trident.
Assuming that aircraft is capable of flight with an engine out situation, they'd most likely react the same as if the engines were mounted further inboard.With wingtip mounted engines, how does one manage an engine out flight or landing?
The jets on the B-36 burned avgas to keep from having two fuel storage systems. As I understand it, 115/145 was hard on the jets and they didn't last long. I guess it wasn't a big problem, since they were only used on takeoff under normal circumstances. There were always a lot of deposits on the tail cone from the leaded fuel, but not being a jet engine expert, I don't know exactly what the internal effects were. I would suspect excessive heat would be a problem.I would point out the B-36 started with only piston engines. It wasn't until the B-36D that jet engines were added.
I would add that, for high performance aircraft, one would likely do better going with a clean sheet of paper design using jet engines. With jet engines, one could normally use a shorter undercarriage and it was worth making design choices for operation at high subsonic speeds.View attachment 669782
Now for WW II we can 'claim' that the piston engines were close to the turbo prop curve.
The orange and green curves didn't exist (n service engines).
We will go with the red turbojet curve, adjust a bit if needed.
Basically a mixed propulsion aircraft could not use both propulsion systems to very food efficiency at the same time.
Altitude will have some effect on this which is why the B-36 worked, kind of.
What complicates things is that the turbo jet had a much better power to weight ratio than the piston engine so it could provide a useful "booster" engine function.
However the turbo jet engines of the time got truly horrendous fuel consumption so you wanted to use them for very short periods of time.
For bombers or transport planes perhaps the "booster" engines did make sense. Even a B-29 could use between 400-800 gallons of fuel just climbing to cruise attitude depending on weight and perhaps a couple of "booster" engines and the fuel for them might have weighed less than running the piston engines for required time.
Most piston planes climbed at around 200mph (or less) where the turbo jet was horribly inefficient.
In single seat fighters the weight penalty of the "booster" engine gets harder to put up with since the proportion of aircraft weight for the power plant/s is a much higher percentage than the with percentage in a bomber or transport.
Any once the fighter is doing much over 500mph the prop is just slowing the airplane down.
With wingtip mounted engines, how does one manage an engine out flight or landing?
Yeah, I recall reading that the French borrowed some ideas from the Germans, the rocket engine initially was based on the Me163's Walther engine and the detachable cockpit was based on the DFS228 and He176 concepts.Dave, the Trident didn't have an ejection seat, the whole forward fuselage encompassing the cockpit broke away during time of emergency. Yeah, not the best idea, but the 50s and 60s were full of real crazy ideas and crew survival appeared to be low on the priority list back then!
Looking at the size of the rudder/vertical stabiliser, I think the best course of action is the handle between your knees, especially if its on take-off.The same way you would in any aircraft, very carefully, of course
Yeah, I recall reading that the French borrowed some ideas from the Germans, the rocket engine initially was based on the Me163's Walther engine and the detachable cockpit was based on the DFS228 and He176 concepts.
Nuuumannn,Actually, I should correct my word usage, not many APUs can be used when the engines are running rather than in the air (I also said not many, not none). There aren't that many aircraft types are ETOPS qualified. In earlier 737s the APU can't be run with main engine power on. I have never worked on 777s, A350s or Dreamliners, so I can't say about them. I've worked on A320s, but not engine systems, only airframe.
Using the APU inflight would only take place during a dual engine shut down. All big jet engines have AC and DC gennies attached, so even if your ETOPS type has a single engine failure, power to essential systems can still be run from the working engine gennies. The other thing for hydraulics is that big airliners have the equivalent to power transfer units (they might be called something else depending on the type) which work independently of the engine driven pumps and provide boost to hydraulic systems (on Airbus aircraft this sounds like a muffled 'barking' coming from beneath the floor of the pax cabin). These can be switched on in flight to aid in flap actuation and depending on the aircraft, undercarriage retraction. The APU would be used to provide bleed air for engine start in a dual engine failure, but in a single engine failure cross starts are possible without APU use.
Yes indeed.Yup, as you know, the French aviation industry survived WW2 by being a shadow German production facility during the war.
Airborne use can be summed up as another level of redundancy.
Simplest answer is operational logistics - mixing spare parts, coolant and different fuels would have been foolish. Would have been just as dumb to put two Allisons to combine with Wright's on a B-17.Im wondering why the idea of a mixed engine plane was never used in combat ? I would have thought with jets being so new at the end of war that more countries would have made either a mixed fighter like the Ryan fireball or a bomber like the B-36 something combing early jet tech with high HP piston engines to increase speed and payload curious to see what people say