Take off MP reduction

Clip4 said:
Yes, your auto can produce that much, but you aren’t running anywhere close to 190 hp cruising down the highway. Even at 80 mph, you are at <50 hp.
Click to expand...

But they're getting those 50 hp out of 2L, not 9L (IO550) and they get run hard to high rpm when cold.. and they don't get the oil changed every 750 miles... and they get cold cranked every morning in January in Fargo with no pre-heat... and they go from 7500 rpm -> 4500 rpm in less than a tenth of a second routinely without require a rebuild... and they meet strict environmental standards that an 'engineer' at COntinental couldn't understand if you read it to him... and they never quit...

But sure, slap some ridiculously low max power rating (seriously 2700 rpm and 33 HP/L is max?!??) on an airplane powerplant and everyone is so impressed that they can be run at 75% continuously... When that 75% converts closer to 25% for an engine that hits more typical peak performance numbers (note: typical, not talking a GT3 here or a racing engine) I find them pretty underwhelming. But I know a lot of people on here will defend these dinosaurs to the death... Have at it..
 
I want to know how that transition from Grumman to Glasair went? And what did you pay for insurance and how did you find it? Curious - is your overall experience broader than just the Tiger, or is that it? IR?

I had a sobering conversation about upgrades with my insurance agent...
 
IMHO - read the POH. In the 182 I fly, it has max throttle and RPM for take off, and then after I have some altitude I reduce to "cruise climb".
 
Clip4 said:
I’d baby the 305 hp 550 and run the hell out of the 230 hp 540.
Click to expand...
If by "baby the engine" you mean "to treat it well", I try to baby ANY engine.

I suspect most of us want to treat their engines carefully. The question is not whether we want to, but how to go about it. That's how this thread started - specifically: is it or is it not good for my engine if I reduce MP on take-off (or right after the wheels leave the ground). And that's where we find many misconceptions. The common belief that a slight reduction of MP is good is incorrect - instead, the corresponding fuel flow reduction moves us towards the red box (higher pressures, higher temperatures). The common belief that a reduction of RPM is good is also incorrect - instead, lower RPM puts the peak internal cylinder pressure closer to top-dead-center of the piston movement.

Intuitively it makes sense - stepping off the gas pedal is good for my car, right, so it should be good for my airplane's engine as well. But it doesn't work like that on take-off. If you want to "baby" your engine, you may have to leave the throttle and prop controls all the way forward. (Again, with a normally aspirated engine and with no POH limitations which say otherwise.)

- Martin
 
You must log in or register to reply here.
Back
Top