Propellor feathering on light twin-engine aircraft
This debate a bout how to feather an engine after a major mechanical fault on takeoff is entertaining but misses a key point in feathering propeller design.
All current single action feathering propellers (light a/c) use an "oil pressure to fine pitch" design.
Loss of oil pressure (IE: the major mechanical failure) above minimum feathering RPM will result in the propeller Automatically feathering as oil pressure drops off (the reason low pitch latches are required).
The only conditions that will result in the propeller completely locking are a loss of oil pressure AFTER the engine has decreased below min feathering speed AND the prop has reached fine pitch (An instantaneous ceasing of rotation with the prop already at fine pitch - very rare for an inflight condition).
Or a mechanical failure of the propeller or governor resulting in the inability to drain oil from the prop (in which case no pilot action will make it feather)
So: Do the feather drill carefully and make sure you identify the correct engine. If you have had a mechanical fault chances are the engine will feather itself before you touch the lever anyway.
All current single action feathering propellers (light a/c) use an "oil pressure to fine pitch" design.
Loss of oil pressure (IE: the major mechanical failure) above minimum feathering RPM will result in the propeller Automatically feathering as oil pressure drops off (the reason low pitch latches are required).
The only conditions that will result in the propeller completely locking are a loss of oil pressure AFTER the engine has decreased below min feathering speed AND the prop has reached fine pitch (An instantaneous ceasing of rotation with the prop already at fine pitch - very rare for an inflight condition).
Or a mechanical failure of the propeller or governor resulting in the inability to drain oil from the prop (in which case no pilot action will make it feather)
So: Do the feather drill carefully and make sure you identify the correct engine. If you have had a mechanical fault chances are the engine will feather itself before you touch the lever anyway.
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Do the feather drill carefully and make sure you identify the correct engine. If you have had a mechanical fault chances are the engine will feather itself before you touch the lever anyway
Thread Starter
The original post discussed the need for instructors to be aware that a major (severe damage) engine failure in a light piston engine twin requires prompt action to feather the propeller before the rpm falls below a critical figure – nominally between 800 and 1000 rpm. The current mantra taught by the majority of flying schools correctly emphasis the need to correctly identify the defective engine before feathering its propeller.
One of the steps recommended is to slowly close the throttle of the suspected engine to confirm it is indeed the correct one to feather. A slow closure is normally effected since a fast inadvertent closure of the wrong (live) engine by a pilot could leave the aircraft with no power even for a few seconds. The resultant airspeed loss would be rapid.
Realistically, the throttle precautionary closure of the suspected failed engine serves no other purpose at that instant except to confirm that the original assessment of “dead leg – dead side” was correct. Some light twin POH recommend the confirmation by use of throttle while others do not mention the technique. While this technique at a safe altitude and plenty of airspeed is acceptable, it is another thing altogether at a low airspeed and low altitude such as the initial climb after lift off.
It was in the days of four engine aircraft powered with piston engines (e.g DC4 Skymasters , Super Constellations or the military Lancaster bomber), that the confirmation of which engine had failed, came into being. For example, if an outboard engine failed, the strong swing towards the dead engine was usually quite obvious through the universally accepted dead leg – dead side confirmation technique. If an inboard engine failed, the swing was less marked although it was still obvious that an engine had failed on one side.
A problem arose if an outboard engine suffered partial failure. In that case from the swing alone it could be easily mis-identified as a failure of an inboard engine although a glance at the engine power instruments would normally give an indication which engine was the problem. So the technique came into being with four-engine aircraft that once the failed engine side had been identified by the dead leg, dead side technique, a slow throttle closure was effected on the suspect engine to confirm which of the two engines on one side had failed. If there was no further yaw when the assumed dead engine was throttled back, then it was generally safe to assume the dead engine had been further identified.
Conversely if closing of the suspect dead engine produced a further really severe swing then both engines on the same side were now out and the pilot had misidentified which was the dead engine.
Even if the two engines on the same side (one of which was truly dead while the other was merely momentarily throttled back and therefore windmilling) were out of action but for different causes, a four engine aircraft usually had sufficient performance to cope for a short time until power was quickly restored to the live engine. But pull back the wrong engine throttle on a light twin with already marginal climb performance on initial climb after lift off, then things soon get out of hand.
The original post resulted in contributors expressing their opinions on light twin take off performance and that is a good thing. This is where Pprune comes into its own with the number of readers having their say while the majority observe and ponder who to believe. But it still boils down to the need to get a defective engine propeller feathered before airspeed loss becomes potentially fatal due to the insurmountable windmilling drag. Reducing the number of actions before feathering is often the key to a successful single engine climb out performance.
In the type of piston engine light twins under discussion and with an engine failure shortly after lift- off, there will invariably be a "dead man's gap" of about 5-10 seconds where the speed and configuration means the aircraft is in a no-man's land for a few seconds. This is not new. Early military aircraft such as the twin-jet Canberra bomber and Meteor fighter sometimes had a 30 knots or more between lift off speed and minimum control speed. In that situation there are so many variables that it is impossible to consider each one before making a decision to forced land straight ahead or attempt a climb out. Of the variables, pilot skill is one vital factor. That means intimate knowledge of the asymmetric performance of his aircraft.
Lack of published single engine performance information in some POH, means rate of climb on single engine may be difficult to quantify; especially if the pilot has never experienced the doubtful pleasure of a real engine failure at that point in the take off flight path. That is the beauty of simulators.
The gear up, flaps up mantra, can be a bit of a trap. If the aircraft type requires a set take off flap (rather than a flaps up take off), and an engine fails shortly after getting airborne and the pilot whips the flap lever to up as part of the gear up, flap up drills, the loss of lift could be serious and the aircraft could sink back into the ground (problem solved re decision to stop or continue
Most pilots would agree that unwanted drag after lift off should be reduced as soon as it is safe to do so. That includes retracting the landing gear once the aircraft has attained a positive rate of climb. That way acceleration towards blue line is quicker. On the other hand, some pilots on initial twin endorsements are advised by their instructors to consider deliberately delaying retraction of landing gear until they guesstimate it is no longer viable to safely land ahead on the remaining runway length (taking into account forward vision over the nose, day or night-time, wet or dry runway, head or tailwind component, pilot reaction time, and maybe no time for the flaps to reach full down if airborne abort).
Rarely are figures published to calculate with any accuracy how much runway is needed for such an airborne abort. Hence the reference to “guesstimate”. Assuming the pilot has been certified competent to operate in command, there is clearly a necessity to making a correct and prompt decision if an engine fails suddenly shortly after lift off in a light piston engine twin. Should he close the throttles and deliberately elect to crash land because he thinks the aircraft doesn't have the performance to climb on one engine? Or does he think he can get away with it as long as he cleans up the drag and that includes prompt feathering of the failed engine?
To summarise: If, immediately after lift off, there is the proverbial loud bang and severe vibration of a badly damaged engine, there should be no need to go through the complete flying school engine failure mantra of the example detailed in the opening post. After all, the mixture levers should already be full rich (or as needed depending on density altitude), the pitch levers should already be at full forward, the failed engine already identified by the subsequent yaw, and no pressing need to confirm which engine has gone by slowly closing its throttle. These are all time wasters at low altitude since the immediate problem is windmilling propeller drag which in some aircraft is greater than the drag caused by an extended landing gear.
The prime identification has already been confirmed by the pilot’s immediate action of preventing further yaw towards the dead engine. Hence dead leg – dead side. Where an engine failure has occurred within seconds after lift off, the pilot may not have the time or airspeed available to afford the luxury of slowly closing a throttle to confirm which engine has failed. The pilot must get it right first time.
Caution: The comments above are personal opinion only. .
One of the steps recommended is to slowly close the throttle of the suspected engine to confirm it is indeed the correct one to feather. A slow closure is normally effected since a fast inadvertent closure of the wrong (live) engine by a pilot could leave the aircraft with no power even for a few seconds. The resultant airspeed loss would be rapid.
Realistically, the throttle precautionary closure of the suspected failed engine serves no other purpose at that instant except to confirm that the original assessment of “dead leg – dead side” was correct. Some light twin POH recommend the confirmation by use of throttle while others do not mention the technique. While this technique at a safe altitude and plenty of airspeed is acceptable, it is another thing altogether at a low airspeed and low altitude such as the initial climb after lift off.
It was in the days of four engine aircraft powered with piston engines (e.g DC4 Skymasters , Super Constellations or the military Lancaster bomber), that the confirmation of which engine had failed, came into being. For example, if an outboard engine failed, the strong swing towards the dead engine was usually quite obvious through the universally accepted dead leg – dead side confirmation technique. If an inboard engine failed, the swing was less marked although it was still obvious that an engine had failed on one side.
A problem arose if an outboard engine suffered partial failure. In that case from the swing alone it could be easily mis-identified as a failure of an inboard engine although a glance at the engine power instruments would normally give an indication which engine was the problem. So the technique came into being with four-engine aircraft that once the failed engine side had been identified by the dead leg, dead side technique, a slow throttle closure was effected on the suspect engine to confirm which of the two engines on one side had failed. If there was no further yaw when the assumed dead engine was throttled back, then it was generally safe to assume the dead engine had been further identified.
Conversely if closing of the suspect dead engine produced a further really severe swing then both engines on the same side were now out and the pilot had misidentified which was the dead engine.
Even if the two engines on the same side (one of which was truly dead while the other was merely momentarily throttled back and therefore windmilling) were out of action but for different causes, a four engine aircraft usually had sufficient performance to cope for a short time until power was quickly restored to the live engine. But pull back the wrong engine throttle on a light twin with already marginal climb performance on initial climb after lift off, then things soon get out of hand.
The original post resulted in contributors expressing their opinions on light twin take off performance and that is a good thing. This is where Pprune comes into its own with the number of readers having their say while the majority observe and ponder who to believe. But it still boils down to the need to get a defective engine propeller feathered before airspeed loss becomes potentially fatal due to the insurmountable windmilling drag. Reducing the number of actions before feathering is often the key to a successful single engine climb out performance.
In the type of piston engine light twins under discussion and with an engine failure shortly after lift- off, there will invariably be a "dead man's gap" of about 5-10 seconds where the speed and configuration means the aircraft is in a no-man's land for a few seconds. This is not new. Early military aircraft such as the twin-jet Canberra bomber and Meteor fighter sometimes had a 30 knots or more between lift off speed and minimum control speed. In that situation there are so many variables that it is impossible to consider each one before making a decision to forced land straight ahead or attempt a climb out. Of the variables, pilot skill is one vital factor. That means intimate knowledge of the asymmetric performance of his aircraft.
Lack of published single engine performance information in some POH, means rate of climb on single engine may be difficult to quantify; especially if the pilot has never experienced the doubtful pleasure of a real engine failure at that point in the take off flight path. That is the beauty of simulators.
The gear up, flaps up mantra, can be a bit of a trap. If the aircraft type requires a set take off flap (rather than a flaps up take off), and an engine fails shortly after getting airborne and the pilot whips the flap lever to up as part of the gear up, flap up drills, the loss of lift could be serious and the aircraft could sink back into the ground (problem solved re decision to stop or continue
Most pilots would agree that unwanted drag after lift off should be reduced as soon as it is safe to do so. That includes retracting the landing gear once the aircraft has attained a positive rate of climb. That way acceleration towards blue line is quicker. On the other hand, some pilots on initial twin endorsements are advised by their instructors to consider deliberately delaying retraction of landing gear until they guesstimate it is no longer viable to safely land ahead on the remaining runway length (taking into account forward vision over the nose, day or night-time, wet or dry runway, head or tailwind component, pilot reaction time, and maybe no time for the flaps to reach full down if airborne abort).
Rarely are figures published to calculate with any accuracy how much runway is needed for such an airborne abort. Hence the reference to “guesstimate”. Assuming the pilot has been certified competent to operate in command, there is clearly a necessity to making a correct and prompt decision if an engine fails suddenly shortly after lift off in a light piston engine twin. Should he close the throttles and deliberately elect to crash land because he thinks the aircraft doesn't have the performance to climb on one engine? Or does he think he can get away with it as long as he cleans up the drag and that includes prompt feathering of the failed engine?
To summarise: If, immediately after lift off, there is the proverbial loud bang and severe vibration of a badly damaged engine, there should be no need to go through the complete flying school engine failure mantra of the example detailed in the opening post. After all, the mixture levers should already be full rich (or as needed depending on density altitude), the pitch levers should already be at full forward, the failed engine already identified by the subsequent yaw, and no pressing need to confirm which engine has gone by slowly closing its throttle. These are all time wasters at low altitude since the immediate problem is windmilling propeller drag which in some aircraft is greater than the drag caused by an extended landing gear.
The prime identification has already been confirmed by the pilot’s immediate action of preventing further yaw towards the dead engine. Hence dead leg – dead side. Where an engine failure has occurred within seconds after lift off, the pilot may not have the time or airspeed available to afford the luxury of slowly closing a throttle to confirm which engine has failed. The pilot must get it right first time.
Caution: The comments above are personal opinion only. .
Just for general info: I did my initial multi at a Moorabbin based school in '09ish and at least then, this is what was being taught:
Blue line speed = decision speed so there is no 'in between zone.' Failure below: close both throttles, land. Failure above with sufficient runway: close both throttles, land. Failure above without sufficient runway: go through the checks.
I was also taught to keep the gear down until there was insufficient runway remaining to land.
Seemed sensible enough to me at the time.
Blue line speed = decision speed so there is no 'in between zone.' Failure below: close both throttles, land. Failure above with sufficient runway: close both throttles, land. Failure above without sufficient runway: go through the checks.
I was also taught to keep the gear down until there was insufficient runway remaining to land.
Seemed sensible enough to me at the time.
Blue line speed = decision speed so there is no 'in between zone.' Failure below: close both throttles, land
The so-called "Decision Speed" quoted by some instructors is a personal speed and nothing else. Same as an earlier post regarding "Decision height" for asymmetric go-around. None is published in the manufacturer's AFM/POH so someone in a flying school invents one and lo and behold it catches on and quoted widely as a measured fact. "When ignorance is bliss, 'tis folly to be wise" comes to mind...
Wasn't actually just made up by one of the instructors, it was in the manual of one of the major Moorabbin schools.
I am fully aware there is no published 'decision speed', but I imagine the reason for using that phrase is to suggest that if you haven't even gotten to Vyse when an engine fails, it's best just to treat it as a single failure and just get it back on the ground.
I would think that fewer would come to grief trying to get a twin landed and stopped before the fence (or go through it if necessary) than trying to get away on one engine before even achieving the best ROC speed. Especially if they are somewhat out of practice on asymmetric flying.
I am fully aware there is no published 'decision speed', but I imagine the reason for using that phrase is to suggest that if you haven't even gotten to Vyse when an engine fails, it's best just to treat it as a single failure and just get it back on the ground.
I would think that fewer would come to grief trying to get a twin landed and stopped before the fence (or go through it if necessary) than trying to get away on one engine before even achieving the best ROC speed. Especially if they are somewhat out of practice on asymmetric flying.
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Wasn't actually just made up by one of the instructors, it was in the manual of one of the major Moorabbin schools.
Someone wrote the flying school manual and probably copied some other flying school manual with a few minor variations. Either way, a flying instructor- possibly the CFI or the CFI before him used his position to push his personal preferences (flying techniques of course) which then are published in the company manuals. As a student at a flying school you are more or less are bound to follow the company published procedures even though they are always a matter of personal opinions.
However, that should not prevent you from questioning those procedures if you have a contrary point of view based upon your own experience and study of the subject.
Yes, I meant it wasn't just my one instructor making it up on his own. It was presumably being taught that way to all the students at the time.
At the place I currently hire from I have questioned a few of their 'local requirements' to the boss, provided evidence as to my position (typically to do with blanket things that don't fit with a specific type/models AFM) and they've had no problem changing things. One of the reasons I go there.
I prefer to get my 'how to' from the manufacturers manuals in general. I presume (hope) they spend plenty of time and money developing the procedures to put in the things.
I mostly made that post to illustrate how things were being taught at a major MB school somewhat recently for the info of those reading to comment on.
I (at my comparably limited experience to many on here) still believe that you're going to have a much better chance looking for somewhere to put it down if you have a failure before getting to Vyse than trying to get everything sorted at a speed which is probably going to give you at best very marginal performance until you can accelerate. Even more appropriate if your asymmetric flying is not quite as current as it should be.
However I'm certainly open to hearing other opinions, your life is going to be far too short if you are going to fly and be obtuse.
At the place I currently hire from I have questioned a few of their 'local requirements' to the boss, provided evidence as to my position (typically to do with blanket things that don't fit with a specific type/models AFM) and they've had no problem changing things. One of the reasons I go there.
I prefer to get my 'how to' from the manufacturers manuals in general. I presume (hope) they spend plenty of time and money developing the procedures to put in the things.
I mostly made that post to illustrate how things were being taught at a major MB school somewhat recently for the info of those reading to comment on.
I (at my comparably limited experience to many on here) still believe that you're going to have a much better chance looking for somewhere to put it down if you have a failure before getting to Vyse than trying to get everything sorted at a speed which is probably going to give you at best very marginal performance until you can accelerate. Even more appropriate if your asymmetric flying is not quite as current as it should be.
However I'm certainly open to hearing other opinions, your life is going to be far too short if you are going to fly and be obtuse.
Great discussion although I always pointed out to students converting onto twins, the only certification requirement was 1%climb gradient at 5000' ( along time ago so the numbers might not be entirely correct). EFATO was best handled by looking for a clear space ahead and controlling it to the point of impact.
A further discussion might be what is actually causing light twins to crash?
CFIT, fuel exhaustion, EF in cruise. Possibly a bit more focus on those areas of piston multi operation might be worthwhile.
A further discussion might be what is actually causing light twins to crash?
CFIT, fuel exhaustion, EF in cruise. Possibly a bit more focus on those areas of piston multi operation might be worthwhile.
FAA safety in light twins
Some flying schools and charter operations still persist with the illusion that light twins can have an engine failure and continue. Maybe yes; maybe no: either way you and your passengers have just become test pilots and observers.
And my personal favourite from the FAA!
The current 14 CFR Part 23 single-engine climb performance requirements for reciprocating-engine twins are as follows:
• More than 6,000 pounds maximum certificated takeoff weight and/or Vso of more than 61 knots. The single-engine rate of climb in feet per minute at 5,000 mean sea level (MSL) must be equal to at least .027 Vso squared. For twins type-certificated on February 4, 1991, or thereafter, the single-engine climb requirement is expressed in terms of a climb gradient, 1.5 percent.
• 6,000 pounds or less maximum certificated takeoff weight and Vso of 61 knots or less. The single-en- gine rate of climb or climb gradient at 5,000 MSL must simply be determined. The rate of climb could be a negative number. There is no requirement for a positive single-engine rate of climb at 5,000 feet or any other altitude.
Regarding climb performance, the light twin with OEI will perform marginally at best and may not be capable of climbing at all under existing conditions. There is no requirement that a light twin in the takeoff or landing configuration must be able to maintain altitude, even at sea level, with OEI.
• More than 6,000 pounds maximum certificated takeoff weight and/or Vso of more than 61 knots. The single-engine rate of climb in feet per minute at 5,000 mean sea level (MSL) must be equal to at least .027 Vso squared. For twins type-certificated on February 4, 1991, or thereafter, the single-engine climb requirement is expressed in terms of a climb gradient, 1.5 percent.
• 6,000 pounds or less maximum certificated takeoff weight and Vso of 61 knots or less. The single-en- gine rate of climb or climb gradient at 5,000 MSL must simply be determined. The rate of climb could be a negative number. There is no requirement for a positive single-engine rate of climb at 5,000 feet or any other altitude.
Regarding climb performance, the light twin with OEI will perform marginally at best and may not be capable of climbing at all under existing conditions. There is no requirement that a light twin in the takeoff or landing configuration must be able to maintain altitude, even at sea level, with OEI.
Landing Gear Selected Up, OEI Climb Performance Inadequate
When operating near or above the single-engine ceiling and an engine failure is experienced shortly after lift-off, a landing must be accomplished on essentially whatever lies ahead. The greatest hazard in an OEI takeoff is attempting to fly when it is not within the performance capability of the airplane to do so.
A recent study revealed a very high success rate for off-airport engine-inoperative landings when the airplane was landed under control. The same study also revealed a very high fatality rate in stall-spin accidents when the pilot attempted flight beyond the performance capability of the airplane.
When operating near or above the single-engine ceiling and an engine failure is experienced shortly after lift-off, a landing must be accomplished on essentially whatever lies ahead. The greatest hazard in an OEI takeoff is attempting to fly when it is not within the performance capability of the airplane to do so.
A recent study revealed a very high success rate for off-airport engine-inoperative landings when the airplane was landed under control. The same study also revealed a very high fatality rate in stall-spin accidents when the pilot attempted flight beyond the performance capability of the airplane.
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I think it is worth pointing out that many an airline doesn't follow what the manufacturer has in the manual for various things. The airlines Operations Manual gets approved and then that is followed.
Aeroclubs are no different.
Aeroclubs are no different.
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Some purely personal observations ..
All too simplistic and typical of some flying schools.
That may be true however simple rules form the basis of SOP - when the action happens and the adrenaline starts pumping is not the time to be going back to developing strategy. A rule-based protocol may well not be the best strategy but it might offer a reasonably considered option in most situations of interest
In any case, Blue line speed is nothing more than best rate of climb on single engine ...
OEI, the speed range for climb capability is narrow and narrows rapidly as weight and DH increase .. rapidly becoming non-existent. Best climb speed sounds like a pretty important number to me.
Another speed quoted in some POH is best angle of climb speed to clear obstacles which still gives you a positive rate of climb although not necessarily as good as Blue Line.
I probably wouldn't like to put my trust in that philosophy ...
There is no published "Decision" speed on light twins.
Depends on what the OEM chooses to include in the POH.
Same as an earlier post regarding "Decision height" for asymmetric go-around. None is published in the manufacturer's AFM/POH ..
But may be. This aspect of OEI operation is looked at with some attention for military acceptance - unfortunately not routinely in civil practice.
Blue line speed = decision speed so there is no 'in between zone.'
Unless the overrun is a cliff drop off or some other dreadful thing ... sounds like a useful rule-based strategy for light twins. Given the rapidity with which one can lose those few knots .. I preferred to target a speed a little in excess of blue line ..
All too simplistic and typical of some flying schools.
That may be true however simple rules form the basis of SOP - when the action happens and the adrenaline starts pumping is not the time to be going back to developing strategy. A rule-based protocol may well not be the best strategy but it might offer a reasonably considered option in most situations of interest
In any case, Blue line speed is nothing more than best rate of climb on single engine ...
OEI, the speed range for climb capability is narrow and narrows rapidly as weight and DH increase .. rapidly becoming non-existent. Best climb speed sounds like a pretty important number to me.
Another speed quoted in some POH is best angle of climb speed to clear obstacles which still gives you a positive rate of climb although not necessarily as good as Blue Line.
I probably wouldn't like to put my trust in that philosophy ...
There is no published "Decision" speed on light twins.
Depends on what the OEM chooses to include in the POH.
Same as an earlier post regarding "Decision height" for asymmetric go-around. None is published in the manufacturer's AFM/POH ..
But may be. This aspect of OEI operation is looked at with some attention for military acceptance - unfortunately not routinely in civil practice.
Blue line speed = decision speed so there is no 'in between zone.'
Unless the overrun is a cliff drop off or some other dreadful thing ... sounds like a useful rule-based strategy for light twins. Given the rapidity with which one can lose those few knots .. I preferred to target a speed a little in excess of blue line ..
Centaurus, I usually really dig your posts. This is all well and good theory but practically, it's a storm in a tea cup, relating to an impossibly rare occurrence.
Firstly - As someone else noted, a catastrophic mechanical failure is reasonably likely to be caused or accompanied imediately by a complete loss of oil pressure - and the prop will feather before the propeller slows and the pitch locks engage.
Secondly - can someone please tell me the last time an Australian registered twin had an engine failure shortly after takeoff where failure to feather quickly was the cause of loss of control and crash? I can think of NONE in twenty years.
Now compare that stat to light twin accidents from
- Inadvertent IMC
- disorientation at night
- fuel starvation (exhaustion or selection)
- weather related phenomena
This is an interesting system technicality and nothing more.
If you have a light twin and want to polish your skills with an instructor, go and do some night circuits at a black hole aerodrome, practice some UAs in a synthetic trainer, or get an instructor to induce the leans for you (easy to do) and learn to fight it and trust the clocks no matter how bad and disoriented you feel.
Statistically, this training is probably 100 times more likely to keep you alive than learning how to quickly feather an engine without running a 5 second drill first, in the unbelievably unlikely scenario that in the first few hundred feet after takeoff, you suffer a catastrophic engine failure and fast loss of propeller rotation while your engine still develops oil pressure.
You're probably statistically more likely to win lotto. Twice.
Firstly - As someone else noted, a catastrophic mechanical failure is reasonably likely to be caused or accompanied imediately by a complete loss of oil pressure - and the prop will feather before the propeller slows and the pitch locks engage.
Secondly - can someone please tell me the last time an Australian registered twin had an engine failure shortly after takeoff where failure to feather quickly was the cause of loss of control and crash? I can think of NONE in twenty years.
Now compare that stat to light twin accidents from
- Inadvertent IMC
- disorientation at night
- fuel starvation (exhaustion or selection)
- weather related phenomena
This is an interesting system technicality and nothing more.
If you have a light twin and want to polish your skills with an instructor, go and do some night circuits at a black hole aerodrome, practice some UAs in a synthetic trainer, or get an instructor to induce the leans for you (easy to do) and learn to fight it and trust the clocks no matter how bad and disoriented you feel.
Statistically, this training is probably 100 times more likely to keep you alive than learning how to quickly feather an engine without running a 5 second drill first, in the unbelievably unlikely scenario that in the first few hundred feet after takeoff, you suffer a catastrophic engine failure and fast loss of propeller rotation while your engine still develops oil pressure.
You're probably statistically more likely to win lotto. Twice.
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Secondly - can someone please tell me the last time an Australian registered twin had an engine failure shortly after takeoff where failure to feather quickly was the cause of loss of control and crash? I can think of NONE in twenty years.
Whether it is a VH rego or not has nothing to do with the subject.
The Dove crash at Essendon. Engine failure shortly after lift off. The pilot was so engrossed in attempting to first retract the gear and flaps that he never got around to feathering the failed engine.
The Cessna 404 (?) crash at Essendon after taking off from runway 35. Total or partial engine failure shortly after becoming airborne. The pilot was so engrossed in talking to and replying to ATC about the engine failure that he never got around to feathering the propeller and due to windmilling drag got below Vmca and flicked inverted and went in.
Cessna 404 crash in Scotland. Engine failure after take off beyond Blue Line speed at the time. Pilot did not feather the propeller and got below Vmca and went in killing all 8 aboard.
I think these accidents illustrate the importance of prompt feathering following engine failure.
relating to an impossibly rare occurrence.
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Tee Emm, I think those accidents illustrate failure to prioritise rather than mechanical failure leading to inability to feather. All except for the Camden accident, which was instructor stupidity.
Whilst you have answered slippery_pete's question, I think he was actually referring to Centaurus' scenario of catastrophic bearing failure leading to a seized propeller. Like you, I'm not aware of any scenarios like that in recent years.
I did once suffer a mechanical malfunction in a light twin, causing cycling of propeller RPM without any change in engine power. I feathered the propeller at the high point of RPM without going through the full drill, for the reasons Centaurus explained. But that was in the cruise, at low workload. I devoted my full & undivided attention to which propeller was malfunctioning and which propeller control I was touching...
Whilst you have answered slippery_pete's question, I think he was actually referring to Centaurus' scenario of catastrophic bearing failure leading to a seized propeller. Like you, I'm not aware of any scenarios like that in recent years.
I did once suffer a mechanical malfunction in a light twin, causing cycling of propeller RPM without any change in engine power. I feathered the propeller at the high point of RPM without going through the full drill, for the reasons Centaurus explained. But that was in the cruise, at low workload. I devoted my full & undivided attention to which propeller was malfunctioning and which propeller control I was touching...
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Perhaps Centaurus' concern also is with those folk who take far too long generally in doing the identification exercise regardless of the nature of the failure ?
I had a simple procedure which worked fine on light twins and the identification and shutdown could be actioned in a matter of a few seconds. I used to go fly some practice time prior to renewals with whomever might have been available to be safety pilot .. on a number of occasions the other chap commented on the short time taken to identify and go through the simulated actions.
On the other hand, I have observed a number of GA pilots (including instructors) taking far too long .. fine at cruise but a recipe for mishap whilse manoeuvring at lower levels ?
I had a simple procedure which worked fine on light twins and the identification and shutdown could be actioned in a matter of a few seconds. I used to go fly some practice time prior to renewals with whomever might have been available to be safety pilot .. on a number of occasions the other chap commented on the short time taken to identify and go through the simulated actions.
On the other hand, I have observed a number of GA pilots (including instructors) taking far too long .. fine at cruise but a recipe for mishap whilse manoeuvring at lower levels ?
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Perhaps Centaurus' concern also is with those folk who take far too long generally in doing the identification exercise regardless of the nature of the failure ?
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Paragraph (a) bears repeating: (a) In the event of an engine failure caused by a major mechanical fault (e.g. seizing bearings due to loss of oil), the rate of deceleration of the engine can be rapid and it is thus imperative that the pilot take immediate action to feather the propeller before the rpm falls to the 1000 rpm region.
Human factors issues though... I can readily accept a need for improvement.
Training for good, quick, emergency response to a critical EF is difficult. I had a good ME instructor who once (near end of training) gave me an unbriefed EF during a radio call. I fixated very nicely on the radio call and learned a good lesson from the result.
Not sure how to fix that problem though, except the same way it was fixed with me. Better instruction.
Last edited by Oktas8; 26th Oct 2014 at 17:56.
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I had a good ME instructor who once (near end of training) gave me an unbriefed EF during a radio call. I fixated very nicely on the radio call and learned a good lesson from the result.
Likewise, shortly after check to the line on my first airline Type, the line captain - a positioning flight with only the two of us on board - pulled an engine on me during the rotation - night but visual.
Bit different when one isn't expecting it, is it not ?
Not terribly good form on his part in the general way of things but the exercise certainly made a good point regarding prioritisation and command thinking - stayed with me thereafter. (Fortunately, I did the appropriate things and it went well.)
Not sure how to fix that problem though, except the same way it was fixed with me. Better instruction
I suggest training and repetitious exposure in a safe environment .. and then a bit more of the same.
How many times, in our early Link training, did the instructor come to the hatch with a coffee (or other innovative distraction) .. just in time to see us go through the level, radial, or whatever ? Eventually, we all got the message - some quicker than others.
The FFS offers a wonderful tool for this sort of conditioning work.
Likewise, shortly after check to the line on my first airline Type, the line captain - a positioning flight with only the two of us on board - pulled an engine on me during the rotation - night but visual.
Bit different when one isn't expecting it, is it not ?
Not terribly good form on his part in the general way of things but the exercise certainly made a good point regarding prioritisation and command thinking - stayed with me thereafter. (Fortunately, I did the appropriate things and it went well.)
Not sure how to fix that problem though, except the same way it was fixed with me. Better instruction
I suggest training and repetitious exposure in a safe environment .. and then a bit more of the same.
How many times, in our early Link training, did the instructor come to the hatch with a coffee (or other innovative distraction) .. just in time to see us go through the level, radial, or whatever ? Eventually, we all got the message - some quicker than others.
The FFS offers a wonderful tool for this sort of conditioning work.
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You're taking that comment out of context. That was referring specifically to an engine failure of such a nature that oil pressure would be lost, but the propeller would *not* feather. Given the mechanics of a light twin feathering system, *that* specific event has a very low probability.