Turbo-charged engine handling
Man Bilong Balus long PNG
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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.
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.
Last edited by Pinky the pilot; 31st May 2008 at 06:34. Reason: Incorrect RPM
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'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
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
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.
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.
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Shock cooling???
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.
Silly Old Git
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
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
Last edited by tinpis; 24th May 2008 at 04:06.
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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!
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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
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
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I like that 2 dogs 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
CW
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
CW
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.
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.
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A lot of old wives tales here
Besides yr at 20000' the air going thru the engine bay is damn cold compared to the circuit at S/L.
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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)
Grandpa Aerotart
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.
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.
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Run ups on the move
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.
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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.
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.
