A nice pair

[Thruster88]

Lycoming io-720's at 400hp a bit big for recreational flying but they do sound great. 

 

 

 

[facthunter]

 They do sound good but I don't know how reliable they are. They probably have a few RPMs that are "don't use". Most motors do but not much is said about it.  Nev

 

 

[old man emu]

Those extra few RPM were called War Emergency Power. Noe the reference to moving the throttle past the "gate stop". In many a recounting of dog fights, you'll see the comment "went through the gate" Note also the administrative requirement for pilots to report the use of Emergency Power to their ground crew. It's astonishing to see that the engines were given a full strip down after 5 hour's use. That suggests that after every escort mission, the engine was taken out. Or it could be that the cumulative time of 5 hours at Emergency Power meant that the engine was overhauled.

 

 

 

 

 

 

Forms 1 and 1A were carried on board all USAAF aircraft during the Second World War. Form 1, Flight Report--Operations , was for recording pilot duty times and aircraft movements. Form 1A, Flight Report--Engineering , was completed by the crew chief to track airplane and engine times, servicing, inspections, and maintenance items. These forms were alternated in bound books of 50 pages, and kept in a metal or wooden (non-strategic material, y'know) box somewhere in the cockpit, and filled out for every flight or series of flights.

 

 

[facthunter]

  Most engines have upper RPM limits where the extreme overspeed is "junk the engine territory", and there are others that require a stripdown if it goes at the RPM for more than a given time.

 

  In my previous post,. the RPM's I'm referring are in the "do not operate in this range" type. where generally torsional harmonics are involved . Complex  engines may have 3 of these bands and you avoid them by running the pitch through them and "not lingering" there when operating the engine. You also have" balanced power " considerations with Radial engines where you don't use high rpms with no throttle (MP or Boost) on as this puts high loads on the crankshaft and the big end bearings. Nev

 

 

[old man emu]

Facthunter,

 

Can you suggest an answer to "could be that the cumulative time of 5 hours at Emergency Power meant that the engine was overhauled."?

 

 

[facthunter]

OME , Its a while since it read up on this, and it varies from engine to engine. For the Gypsy Major its an RPM and time (at the time) There's two figures and one (the high one is scrap it if you exceed it. I'm guessing but I think it's about 3500 rpms for an engine  that normally about 2500 or less . That's not particularly High RPMs but the engine is not robust. the other one is lower and there's little point guessing and it's probably 5 minutes. I recall NO mention accumulating times. These engines never had variable pitch props so any overspeed would have to be associated with a high IAS and presumably some aerobatic maneuver gone very wrong.

 

 the other one was to do with a Cessna 310 Continental 520?  which has feathering and CS props. THAT info should be in the aircraft POH.

 

  The METO( Maximum except take off) for a time (usually 5 minutes) is to do with using the engine as a heat sink where you need it to clear something like when another engine fails. The military settings resulted in a reduced time to overhaul TBO, applying which could halve the normal figure or even  more. The overboost gate was even more  than the military settings. I've never been involved with that. Overhaul time for military engines are quite low, compared with the same engine used to civilian figures. Some peculiar operations , like diving a DC-3 though a hole in the clouds in PNG with pitch fine and throttles closed ruined engines. prematurely. Nev

 

 e

 

 

[spacesailor]

" but I think it's about 3500 rpms for an engine"

 

Makes Stan Sainty's motor look good, No Great !.

 

" “The more fuel you can burn the more power you can make but if it spins the tyres and revs up too much it will hydraulic and blow up. If it has too much load on it, it will be lean and blow up. At wide-open throttle the engine will use 65-80 gallons per minute. That’s two 44 gallon drums per minute.”

 

I tried to get max RPM,  I know it's out of this world, more so than the 6000 hp output. (I think over 2,000RPM, But I could be dreaming)

 

So a quick look at the best Australian motor to date, ( with a son-in-law )

 

And to see it Run !.  Sainty4.7seconds.html

 

spacesailor

 

SaintMotor.html

 

SaintMotor.html

Sainty4.7seconds.html

[Student Pilot]

 They do sound good but I don't know how reliable they are. They probably have a few RPMs that are "don't use". Most motors do but not much is said about it.  Nev

720's are very reliable. They will run all day at max continuous. Usual fitment for Fletcher, you wouldn't get a much harder engine life with a take off every 5 or 6 minutes. These engines run to their TBO on AG ops no problem. Trouble is cost of overhauls, very expensive. They do use a lot of fuel but if you want power you have to pay for it.

 

Those in the picture Freddie's?

 

 

[facthunter]

They are just the 540 with two more cylinders added, but longer cranks always bring extra problems of torsional vibration damping. Nev

 

 

[Guest deanfi]

regarding the war emergency power , I believe there where quite a few ways this extra power was achieved  .

 

some I can think of where methanol-water injection , nitrous oxide injection by the germans , Raising supercharger boost pressure  and also just opening the throttle more , no doubt there where other ways also , I guess the p51's and such running around Reno pulling 135 inchs are operating at war emergency power plus some