Turbo-charged engine handling

[THE IRON MAIDEN]

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?

[Cap'n Arrr]

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!

[Chadzat]

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

What CHT's is it running at 29"?

[THE IRON MAIDEN]

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

Not sure what the CHT was sorry.

[tio540]

"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.

[Capt Fathom]

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! :(

[kalavo]

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*

[Fonz121]

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.

[dirka]

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:

[willnotcomply]

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.

[Defenestrator]

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:

[THE IRON MAIDEN]

thanks guys

seems to be what i thought. :ok:

[ranfurly]

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

[Tankengine]

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

[tinpis]

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.

[FullySickBro]

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!! :}

[PLovett]

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.:}

[Konev]

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

[ernie blackhander]

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.

[Gun_Knutt]

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.

[tinpis]

I treated a Queenair engine like it was a bucket of nitro-glycerine ernie :hmm:

[Pinky the pilot]

A company I used to do some casual work for had a fleet of Chieftains and the company policy was 31'' 2300rpm for the cruise. This setting was maintained in the descent (500fpm) until reaching the circuit height of the destination airfield.

Upon reaching the circuit height power was steadily reduced to 25'' and maintained to short final, with the rpm being increased to 2400 (climbing rpm) just before turning final.

Power was slowly eased off from 25'' from about 100' above the ground.

In all my association with this company (about three years) there was not one instance of cracked cylinders.:ok:

[Capt Wally]

'tinpis' I think you may be closer to the thruth than most think in here.
Apart from sudden engine pwr changes & closed taps at TOD careful engine handling doesn't have to be that complexe as some have shown in here. These are air cooled engines & are designed to some degree for possible over cooling on a typical decent. Mr Conty & Mr Lyc knew that you can't get every pilot to do exactly the same thing when it comes to engine handling so they built a strong engine that with some basic common sense care didn't need babying. Am sure most in here (the old salts) have stories to tell about cracked cylinders etc but that was mainly caused by poor engine handling by way of long term damage generated by leaning techniques & poor maintenance (Eg. poor fitting cooling baffles etc). I've done a few years in the eng O/Haul game & saw some shocking engine installations where there where almost no cooling baffles left, that's where shock cooling really comes into play.
As usual personal opinions only


CW

[romeocharlie]

1''/minute - that is how two companies in Cairns have run fleets of 404's/402's for years, and neither company has a great deal of cracked cylinders.

There is a stopwatch in many aircraft straight in front of you, just hit it every minute as you bring back an inch, and you shouldn't have any troubles - I personally think this is a better method as to 1''/1000' as the rate of descent can vary from a/c or on different approaches.

[youngmic]

John Deakin aka Pelicans Perch on the Avweb site had a 5 part series on handling turbo charged flat engines.

May well be the definitive guide on the matter.

[bushy]

I remember watching a LAME running the engines of a 402 during maintenance and finding rough running. The engine was hot so he could not do the usual trick of looking for the cool cylinder to find the offending cylinder, so he hosed down the engine to cool it, and started again with a cold engine. I often saw him hosing down hot engines.

[tinpis]

The problems I heard of on big LYCs was from CASE cracking around the cylinder retaining studs
Nothing to do with cooling or fancy throttling
The only engine Ive ever flown that required careful throttle control on descent was a bloody Dart

Edited to add:
Hey..if thats what the AC owner requires..... do it
It would surprise me as Wally says,that any two GA pilots were doing the same thing anyway http://www.augk18.dsl.pipex.com/Smileys/laughpound.gif

[willnotcomply]

It has always been my belief that,"if you look after the equipment, the equipment will look after you". Leave the a/c in good shape for yourself and the next guy to fly it. My generation call that airmanship. It takes effort to do things well, with consistency. That is the difference between the professional and a weekend warrior. Treat all engines with respect, piston, jet or otherwise!

[HireTheBetter]

When i used to fly high powered pistons, the 1inch per minute was always a good guide. Keep in mind though that once you start a decent the indicated airspeed will increase, therefore the airflow around the pistons will also increase cooling them quicker. So my theory was to never reduce power for the first 2-3 minutes of decent. If cruising at lower levels, this often meant reducing power slightly before decent so that you would arrive in the circuit with the appropriate power setting. Another thing to keep in mind is that when you arrive in the circuit, the airspeed will then come back and the cooling effect will be reduced allowing for faster power reductions at this point due to the slower airspeed.
So if you have left your power reductions too late in the decent then dont reduce by more than an inch per minute in the decent but wait until your in the circuit and slowed down to bring off the power in faster intervals.

As it has already been said, look after the equipment and it will look after you but also operate the aircraft as you have been instructed by the owner/operator, although this can sometimes be contradictory to each other!!!! Commonsense will always prevail.

HTB

[Two_dogs]

FLY IT LIKE YOU STOLE IT! :E

Two Dogs

[Capt Wally]

I like that 2 dogs:ok: In other words flog them, don't baby 'em:) There air cooled engines, thay are meant to have air rushing thru the engine bay, hence the baffels & cowls flaps to control same. Besides yr at 20000' the air going thru the engine bay is damn cold compared to the circuit at S/L.
A lot of old wives tales here:bored:


CW

[Stationair8]

Make sure your instructor demonstrates the following during the endorsement:

1.How to taxi at 2000 RPM while riding the brakes,

2. Taxing at 2000 rpm with the crew door open past the Royal Vic Aero Club(Raybans and whit shirt with gold bars) on a Sunday afternoon,

3. Make sure you conduct the engine runups with the passenger door open on a Navajo,

4. Make sure he gives you a lecture on engine cooling and then flies around the circuit with 30"Map, and maintains that until landing or in some case after landing,

5. Make sure he demonstrates the technique of rolling of on to the 90 degree taxiway while still doing at least 50 knots.

6. And the tried and true method of doing engine runups while taxiing.

[youngmic]

A lot of old wives tales here

Oops and there's the start of another one :=

Besides yr at 20000' the air going thru the engine bay is damn cold compared to the circuit at S/L.

Yeah but cooling is less efficient than at SL, density is the key to it. :ok:

[ForkTailedDrKiller]

6. And the tried and true method of doing engine runups while taxiing.

and what's wrong with that?

Dr :8

[T28D]

Absolutely nothing in fact it is far better for the propellor to have it absorb power whilst rolling than it is standing still, has a lot to do with torsional stress on the blades and consequential transferred stress into the hub ( Spider)

[Chimbu chuckles]

The air might be cold at FL200 but there is precious little of it. FL200 and above is where intercoolers REALLY start earning their keep.

The old rule of thumb about 1in MP/1000' (or minute) is a good one...until you get to 25in MP and then leave it until reducing to 18in odd on downwind.

As soon as you get below 29 inches MP on descent the turbo is not doing a whole hell of a lot. The engine/turbo will never be cooler than it is as you touchdown...every minute you spend 'cooling' it down after parking is actually heating it up via radiant heat from the engine, which is also heating up as you sit there cooling it down.

[Tankengine]

Engine run ups while taxying -

Try feeling brakes afterwood if you are riding them!!:eek:

If not on brakes then ok.:)

[willnotcomply]

Run ups during taxi certainly do have their place. Namely gravel strips, most have no provision for run ups. An old boss (a LAME) use to endorse the practice, citing that brakes were alot cheaper than props. On that note, it is wise to park the a/c in a position that will require min power to taxi. ie Don't park with the nose facing uphill, yes it happens alot.On your walkaround, clear the area of large rocks around the props with your boot.

[Captain Nomad]

While idling on the ground after landing may not really provide 'cool down' (although a JPI in one machine I flew still indicated a rate of cooling which of course was less than at touchdown but still cooling) don't forget that turbo has been spinning awefully quick and providing some lube in the form of running the engine with sufficient oil pressure will help the life of your turbo bearings. Even though some parts might be warming up it also provides an 'evening out' of engine temperatures throughout the engine before shutdown which according to at least one LAME is very beneficial.

Managing cowl flaps can help a lot. One method which can help is to open them gradually for extra cooling before starting the descent then close them again while reducing power and descending - helps to provide a good cooling gradient even if you have to do a relatively quick descent becuase you are starting the cooling process early. A JPI monitor set to 'cooling' on descent makes the process of management a lot easier - also helps you to know what has the greatest affect in your particular aeroplane. Winding down the RPM on descent as has been mentioned will help reduce glazing which is also worth considering.

[Capt Fathom]

Run ups during taxi certainly do have their place

Particularly in a floatplane......:uhoh:

[sms777]

I have owned and operated a Queenair for ten years and spent many hundreds of hours flying it up north. I have treated it like "tinpis" said like a bucket of nitro-glycerine and got full life out of my engines.
Smooth and planned power reduction is the key to long engine life and i have never babied it on take offs either, pushing 48 inches every time reducing it to 45 only with the gear cuming up. It is good to know you have every horsepower there when you need it. Never beleived in reduced power take off in a piston.

[tinpis]

The only failure I had with a PA31 turbocharger was the turbo outlet pipe retainer fell off
Loud bang...**** pants... :ooh:

[Chimbu chuckles]

Nomad true...but after about 1 minute or so the temps will be heading upwards again...by 3 minutes they will be REALLY going up. If operating with a JPI or similar I would suggest 1 minute or when the temps start climbing shut everything down.

I suspect people took the general rule of about a minute to stabilise temps/reducing turbo impeller RPM and figured if I minute was good 3 was better. They misunderstood stabilising for cooling and a new 'old wives tale' was born.

[Captain Nomad]

CC - agreed. I was just having visions of people doing what one guy up here does. Flying a 404 around with no warming up - just blasting off and then swinging into the parking bay after landing and killing the mixtures as soon as the wheels stop rolling! And they wonder why they have to pull the cowlings off after every flight to fix things... :hmm:

[Nivo]

1. If the aircraft belongs to someone else - do what they want.

2. If the aircraft belongs to you - do some reading that is based on facts. This (http://www.avweb.com/news/pelican/182107-1.html) might be a good place to start.

cheers,

Nivo

[kalavo]

If the aircraft belongs to you - do some reading that is based on facts. This (http://www.avweb.com/news/pelican/182107-1.html) might be a good place to start.

Speaking of "this" did anyone go to the engine management course CPAA flew John Deakin & Co. to Australia for or has anyone done their online course?

[Stationair8]

At the end of the day the objective of the exercise with any aircraft is to get the engine or engine's through to their TBO, without having to pull cylinders off, change exhaust valves or repair crankcases etc.

Over many years of working in the industry, I have seen people try and save a quid on fuel by leaning engines incorrectly only to wonder why at the next 100 hourly they have to change a cylinder, don't start me on reduced power take-offs just think about the C402 at Essendon, likewise some operators can get full life out GTSIO's in C421 or C404 yet other operators aircraft spend most of their life in the hangar with engine dramas.

[Centaurus]

Many pilots love myths and quickly adopt them as facts. Shock cooling myths endure the longest. Makes you wonder why flying through rain does not cause immediate cracking of cylinders due uneven cooling. After all, rain and slipstream chill factor really lowers the water temperature hitting the cylinders which in turn results in uneven surface cooling at a rapid rate yet we don't have piston engine singles and twins falling out of the sky.

[sms777]

You do have a point there, but with a prop spinning 2400 rpm in front of your cylinders i do not think there will be many raindrops actually hitting the pots....
Just a thought....
Anyone care to correct me?

[tinpis]

Some got through on this (http://www.pprune.org/forums/showpost.php?p=3907576&postcount=30) flight :ooh:

[Ex FSO GRIFFO]

"The DC-3s we were flying at that time were fitted with Wright Cyclone engines. These engines had a characteristic of stopping in torrential rain which we frequently encountered over the Coral Sea; a frightening experience, especially as we carried no survival equipment.

Fortunately they would regain power as we descended to lower levels. It was quite some time before we discovered the cause of this phenomenon.

Apparently there was so much water being drawn into the carburettor air intake that the engines couldn't handle it, so by selecting hot air which was normally used for carburettor de-icing we could overcome the problem.

The Pratt and Whitney, which was the optional engine for these aircraft, did not have that problem but we found them to be less reliable in the conditions under which we operated."

From Peter Yule's "The Forgotten Giant Of Australian Aviation" -
The Story of A.N.A.

Not that I have ever had the pleasure, but I was under the impression that DC-3 pilots LOVED the P&Ws over the Wrights.......

Anyhow....thats rain too!

G'Day 'Tin',
That too sounds familiar, like I think I have read that somewhere. Source?

I wonder how rain like that would affect today's 'Contis' or Lycomings?
I have flown both types through what I thought was 'heavy' rain (Obviously not as heavy as above) at times - short bursts only - with no noticeable effect.

Cheers:ok:

[tinpis]

Ex FSO GRIFFO sorry I didnt add a source its in the Pixie reunion thread among stories
As far as Contis go I sure soaked a Baron a few times while based in Daru in the Western districts without a hiccup
Solid IMC pissing pick-handles Daru -POM was a normal.
Im sure a P&W if you could supply it with fuel, would run underwater :ok:

[youngmic]

The smaller 1340/985 used to sometimes get water into the harness around the front, caused them to wobble a bit. Never had it from rain, usually in the pub in front of the fire by then.

Pressure washer would do it if you weren't careful and because it's in sealed (?) alloy tubes once it got in it took for ever to dry out.

[Centaurus]

I flew many hours in the RAAF Convair 440 Metropolitan's. One of them (A96-313) was not equipped with weather avoidance radar and we experienced occasional problems with Cb penetrations. On at least one occasion the cylinder heads temps dropped right back and this was caused by heavy rain. I don't recall servicing problems with cylinders caused by lots of water entering the cowls, although we sure had ignition harness problems. Also significant spark plug fouling caused by 115/145 octane fuel which caused leading up with prolonged ground operation. Couple of impressive start up fires too.

[Fantome]

Why did ANA have Wright Cyclones in their DC-3s? Because Ivan Holyman bought a hangar full of them from the Yanks towards the end of the Second World War and converted the whole fleet. (The surviving VH-ABR case in point.)

Incidentally, Ivan was, from various accounts, at times a silly old git. Too stingy, he refused to fit wipers on the RH windscreen causing the pilots to threaten a stoppage. Another time he issued an ops memo to all aircrew saying he would not tolerate the use of obscene shorthand in maintenance logs. (Thought U/S stood in pilot parlance for up the ****!) Source: "Outback Airman" by Harry Purvis. Harry was one of Holyman's prewar pilots and a founder of the union that preceded the AFAP.

[Pinky the pilot]

Solid IMC pissing pick-handles Daru -POM was a normal.


Only ever did two POM-Daru runs Tinpis but both times it was the above somewhere along the way!:eek:

Always seemed claggy around Kikori/Kuri though.