Turbo-charged engine handling
 

Just a quick question. How many inches/min should you bring back a 350HP turbo charged engine?

is 29" to idle (landing roll) in 3mins too short?

Have never flown one in my life, however I believe it is 2"/min pre ToD, and once below 25" can be handled like a high performance NA engine.

Does this mean you bought a Mojave?:ok:

Edit: Interested to know what the correct technique is!

How about you tell us at its next 100hrly!! :ok:

What CHT's is it running at 29"?

yep the mojave is here, and no i wasnt flying. ( just watching )

Not sure what the CHT was sorry.

"Have never flown one in my life, however I believe it is 2"/min pre ToD, and once below 25" can be handled like a high performance NA engine."

I don't know either, but thought I would post anyway.

This is the sort of information that was passed on during endorsements.
Sadly, a lot of the people conducting the endorsements these days have no idea either.
The experience pool has all but dried up! :(

This guy has more than a few opinions...

http://www.avweb.com/news/pelican/182544-1.html

...but their his opinions, if you listen to em, listen because they make sense not because of their "experience" (same rule of thumb for anyone... 1000hrs or 30,000hrs - not much difference when it comes to operating pistons and 29,000hrs out of the 30 are in Jets :)

The GFA also had some interesting notes on aerotowing and engine failure rates on engines that idle and descend at Vno compared to those at 2200rpm or higher at Vno.


My advice... run the engine the way the owner wants the engine run. It's their money, they're the ones that pay for the maintenance, it's their choice... even if you "know" better.

If it was my engine, I'd care about climb and proper use of cowl flaps. Cruise and Descents, honestly... what are you going to do at 29" and/or 75% or less power. That said, there's a lot of inertia in that engine, be gentle when you do make changes dont rip the throttle out of the firewall. Thing I'd be more concerned about is running it often - look at how many Flying Schools regularly make TBO, and look at how many Taxi's get significantly more km's by keeping the engines going 24/7 even when engines in both environments get "abused" signfiicantly.

My two cents and *more fuel on the fire*

I was taught (and use) the 1 inch per minute rule. We use 31" in the cruise and start decreasing power 6 mins before the CCT where we want 25". Thats for 350HP Turbo charged engines. Was taught that by someone who has very good engine care traits.

Just do an inch per thousand feet. If your flying at low altitudes, just use common sense and start bringing it back early before the circuit. Don't let anyone tell you it's hard :ok:

Thermal shock is the enemy here. You obviously don't reduce from crz pwr to idle at 10000ft. This will crack pots! 1"/min(500ft) reduction on descent works well. This will look after CHT's. Once at circuit ht, you are "out of the woods". As in any a/c though, be smooth with any inc/dec pwr.

It's not rocket science guys (hope that doesn't sound arrogant). Trickle off 2 inches of MP for every 1000' on descent. Do it smoothly as you would with an engine that is not turbo charged. Plan to arrive in the circuit with around 20 inches on the tap. It's all about cooling. If you need to give it a skinfull at this point it'll be ok. Like everything do it smoothly. Albeit a long time ago we never cooked a donk through ignorance. Look after the engine and it'll look after you.

D:ok:

thanks guys

seems to be what i thought. :ok:

we operate three different types over 300hp and standardise on reduction 1" per minute 8 minutes out

Also the FIRST 25-50 degrees of cooling is the most important to be slow!

I know of a fleet of Chieftans that were FLOGGED
Never even heard of power reduction carry-on
Never had a SINGLE issue with the engines apart from mags and other things falling off
In PNG all 402s in my day anyway,were caned CONSTANTLY
Never had a problem.

Man I enjoyed flying the Mojave. A man's aerplane as they say and requesting flight levels always gave a sense of self importance :E

I found an inch/ min, thousand ft etc etc all worked well when everything was tickety boo and even when it goes tits up e.g. after a go around then a recircuit to land then bringing the power back to 2 or 3 smooth motions over the course of the circuit never bothered her too much...

Happy flying!! :}

Thanks tinnie for some words of sense.:ok:

I suspect that there are more old wives tales about "shock cooling" in aviation than any other subject, especially in relation to operating turbo engines.:ugh: I also suspect that there are more problems with going from low power settings to high too quickly than the other way.

That said, operate them the way the owner wants them operated and also take into consideration that abrupt power changes often scare the beejeesus out of pax. They need more careful handling than the engines.:}

this is basically how i have been taught to hand the piper senica II.

tinpis & plovet the theory of power on decents is not really an old wives tale. The big dirty old lycos handle a bit more abuse than the conts, never really seen many turbo lycos that had been treated with great love and care (skydive and remote wa rpt nevergo's and chieftians) and they just seemed to take it in their stride. But treat a highly strung and lightly built engine like a gtsio the same way and you might be noticing a few expensive repair bills. Apart from keeping the heat in the engine to prevent shock cooling you are also maintaining a manifold px suitable in keeping sufficient px on the pistion rings which will maintain them pressed against the cylinder wall preventing ring blow by and cylinder glazing. As for after landing, keep the rpm up and allow a good cool down period (3 minutes was recomended), not necissarly to cool the engine but to allow the turbo to have a bit of a chance to cool and not get carbon ladened by the oil cooking on the bearings.

Nicely said ernie
 

when I was in Alice, a Chiefy turned up to start for Air North(I think) and they found 10 cylinders were cracked. It happens... usually from knuckle heads who couldn't give a preverbial.