Engine Damage Turbo Prop.
Joined: Jul 2013
Posts: 193
Likes: 0
From: equatorial side of the Polar Jet
NH~zero.This means the HP turbine has ceased and therefore engine has ceised. Also you will observe erratic indications on other instruments..and possibly some noise and vibration during seizure.There will almost certainly be High ITTs, dropping torque(or over torque during seizure befomage) and hardly any windmilling of the prop.Oily smell might seep through the aircon system and accompanying smoke.But the one most reliable indication in the cockpit is low to zero NH.
Last edited by Trackdiamond; 23rd October 2013 at 11:55.
Joined: Jan 2008
Posts: 2,296
Likes: 305
From: All at sea
A smooth run-down could be fuel leak, fuel control, fuel starvation or possibly ice ingestion, flying in very heavy precipitation, prolonged negative 'g'. None of which could be considered 'severe damage'. Whether one should attempt a relight in such a situation is a moot point. Personally I don't like the idea of relighting engines because they are not supposed to run down, but if a worse emergency could develop from not attempting a relight, why not have a go? Or if you did something silly like run a tank dry, of course you would relight and hope no-one noticed.
Severe damage suggests something broken, blades, bearings, near total loss of oil or perhaps an over-temperature due to mis-handling or fuel control problem. Bird strike will do it, and FOD is another possible culprit if on the ground - though the PT-6 and similar designs are fairly resistant to birds and FOD. Lightning strikes have been known to cause considerable damage to PT-6 engines in particular.
Indications of severe damage could include vibration, high TGT/ITT/TIT/EGT, possibly very high oil temperature, possibly the smell of oil or smoke through the air conditioning, a fire warning indication. Slow rotation of the power turbine accompanied by high temperatures is very bad news and of course no rotation of any section that is supposed to be rotating means it is seized and very, very dead. Or you are flying too slowly and about to become very, very dead.
Don't fall into the trap of mis-diagnosing low oil pressure as a failure in itself when it is often simply a result of the engine having already run down. Turbines will run for some time on hardly any oil pressure, provided that some oil is still in the system.
Obviously a relight must NOT be attempted if any of these indications are present.
Severe damage suggests something broken, blades, bearings, near total loss of oil or perhaps an over-temperature due to mis-handling or fuel control problem. Bird strike will do it, and FOD is another possible culprit if on the ground - though the PT-6 and similar designs are fairly resistant to birds and FOD. Lightning strikes have been known to cause considerable damage to PT-6 engines in particular.
Indications of severe damage could include vibration, high TGT/ITT/TIT/EGT, possibly very high oil temperature, possibly the smell of oil or smoke through the air conditioning, a fire warning indication. Slow rotation of the power turbine accompanied by high temperatures is very bad news and of course no rotation of any section that is supposed to be rotating means it is seized and very, very dead. Or you are flying too slowly and about to become very, very dead.
Don't fall into the trap of mis-diagnosing low oil pressure as a failure in itself when it is often simply a result of the engine having already run down. Turbines will run for some time on hardly any oil pressure, provided that some oil is still in the system.
Obviously a relight must NOT be attempted if any of these indications are present.
Last edited by Mach E Avelli; 23rd October 2013 at 10:51.
Joined: Jan 2003
Posts: 811
Likes: 0
From: The Heart
A big bang and a big cloud of white smoke was the first thing that caught my attention when the aircraft I was flying suffered severe damage to its PT6.
The power lever was also stuck and the prop began causing considerable drag which made the climb performance suffer somewhat, it being a single engined aircraft.
Then I noticed the rpm to be zero and the ITT falling so I was sure something had ahappened.
On the other hoof, the fuel flow was zero so I was sure this would not be the limiting factor in dealing with the situation.
The power lever was also stuck and the prop began causing considerable drag which made the climb performance suffer somewhat, it being a single engined aircraft.
Then I noticed the rpm to be zero and the ITT falling so I was sure something had ahappened.
On the other hoof, the fuel flow was zero so I was sure this would not be the limiting factor in dealing with the situation.
Joined: Mar 2012
Posts: 20
Likes: 0
From: On the couch
Maybe a bit in a different direction than as posted above, but a broken prop drive shaft could also be considered severe engine damage. Meaning the engine runs perfectly fine, though no propulsion. Normal ITT and Nh, but no Tq 
Joined: Mar 2008
Posts: 555
Likes: 0
From: Western USA
Mach E Avelli
Don't fall into the trap of mis-diagnosing low oil pressure as a failure in itself when it is often simply a result of the engine having already run down. Turbines will run for some time on hardly any oil pressure, provided that some oil is still in the system.
Obviously a relight must NOT be attempted if any of these indications are present.
Obviously a relight must NOT be attempted if any of these indications are present.
When at a previous company we had a PT6 on a Twin Otter go from about 10-15# of torque to seizure in the blink of an eye. Thankfully it wasn't during the climb when at 40# of torque.
