The P-Factor Factor

[XBe02Drvr]

I'm new to this nice site... have enjoyed wandering around it before registering. Lots of great info presented.

Welcome aboard, Frank! Always great to have another CFI onboard. Congratulations on the most thorough and concise explanation of left turning tendencies I've seen. Better than Kershner, Jepp/San, or any of the other texts. As you've probably already discovered, we have a great bunch of folks here with a wide variety of experience and perspectives, not to mention nationalities.
Wetting down in the forward (dirty shirt) wardroom at 1800. Uniform: undress khakis or flight suit.
Cheers,
Wes

 

[Frank G.]

Great post, apart from the above "bit" this is part of the human condition, learning something is one thing, you can learn somethings so well they become almost reflex actions. Unlearning a reflex action and replacing it with another action can be difficult.

You just about hit the nail on the head with "unlearning" a habit-pattern. There are lessons to be learned with this unfortunate accident; read on if you wish.

I was next in line to take off behind the departing Tempest. My student and I drooled at its beauty and power-- it's another favorite airplane of mine. Our wonderment turned to shock as we saw that magnificent bird rapidly snaking and skipping down the runway until the pilot literally pulled it off the runway.... prematurely. This action lead to an immediate yaw/bank to the right and snap-stall with an almost immediate ground collision which separated the engine and cartwheeled the airplane.

The Tempest lost its main landing gear during the cartwheeling before slamming onto its belly and sliding to a stop mostly intact. I taxied rapidly over to its resting place and we exited our plane. We jumped onto the wing and saw that the pilot was unconscious and still strapped in.

My student and I tried to locate the emergency canopy release handle and could not (we found out later that it had been removed due to cosmetics!). We tried in vain to break the canopy open and finally had to abandon our efforts because of smoke and flames erupted under the airplane. The cockpit filled with a dark grey smoke and the flames began to crawl around the wing's leading and trailing edges; my student and I exited the area by running toward the wingtip and jumping off upon reaching it. All we could do is watch as the poor pilot and once beautiful Tempest were consumed by fire. Very sad.

Here's what was revealed with a little investigation:
1. The pilot had flown the Tempest once before and had joked about its takeoff characteristics with his warbird buddies. It was his second warbird; his first was a beautiful Corsair. Habit patterns were in conflict with what was necessary to fly the Tempest.
2. The pilot refused to wear a hardhat because he felt the leather helmet was sufficient. Had he he may not have been knocked unconscious during the crash sequence and could have escaped or aided in his rescue.
3. The pilot did not like to perform takeoffs with his warbirds canopy open (for egress just in case). This is just plain dumb in my opinion.
4. The pilot had a habit of refusing dual instruction because he believed he was capable of mastering whatever airplane he desired to fly after reading the AFM/POH. Call it arrogance or ego... but he was eventually bit hard by this attitude.
5. The pilot disregarded SOP's as well as decommissioning safety items he felt were unnecessary. No idea how it was FAA certified for ops. Probably never seen by the FAA knowing how this fellow behaved.

The accident left a widow who also flew. She was the one who was injured in the PT-17 accident I mentioned earlier. This took place about a year after her husband died in the Tempest accident. After her recovery she sold all the airplanes, their successful business and moved to somewhere in AZ.

Not telling you folks this to be a downer... just to give you a little info on pilot behavior/attitude and details that could have been avoided had BOTH pilots been open to dual flight instruction and recurrency training. The wife was lucky... she survived her event and was either scared away from flying or realized she wasn't the type who should be flying.

 

[Frank G.]

Welcome aboard, Frank! Always great to have another CFI onboard. Congratulations on the most thorough and concise explanation of left turning tendencies I've seen. Better than Kershner, Jepp/San, or any of the other texts. As you've probably already discovered, we have a great bunch of folks here with a wide variety of experience and perspectives, not to mention nationalities.
Wetting down in the forward (dirty shirt) wardroom at 1800. Uniform: undress khakis or flight suit.
Cheers,
Wes

Thank you Wes. Bill Kershner was a good friend... a spinning maniac.

 

[XBe02Drvr]

Thank you Wes. Bill Kershner was a good friend... a spinning maniac.

A tale-spinning maniac! At a NIFA competition at Embry-Riddle in 1976, I saw him entertain instant crowds of collegiate aviators with vignettes of aerial foibles every time he paused for a snack or a drink of water. They followed him around like the Pied Piper, and every time he sat down a flashmob would form and the tales would resume. He was coaching one of the teams (UTenn, I think), but he was treated like he was head of the International Olympic Committee. I never did get to speak with him personally.
Cheers,
Wes

 

[Frank G.]

A tale-spinning maniac! At a NIFA competition at Embry-Riddle in 1976, I saw him entertain instant crowds of collegiate aviators with vignettes of aerial foibles every time he paused for a snack or a drink of water. They followed him around like the Pied Piper, and every time he sat down a flashmob would form and the tales would resume. He was coaching one of the teams (UTenn, I think), but he was treated like he was head of the International Olympic Committee. I never did get to speak with him personally.
Cheers,
Wes

Hi Wes,

That he was too! He had plenty of experiences to draw from. He was quite a guy.... loved flying, teaching it and life. Bill helped many a budding and already "budded" pilots.

Later,

Frank G.

 

[pbehn]

You just about hit the nail on the head with "unlearning" a habit-pattern. There are lessons to be learned with this unfortunate accident; read on if you wish.

I was next in line to take off behind the departing Tempest. My student and I drooled at its beauty and power-- it's another favorite airplane of mine. Our wonderment turned to shock as we saw that magnificent bird rapidly snaking and skipping down the runway until the pilot literally pulled it off the runway.... prematurely. This action lead to an immediate yaw/bank to the right and snap-stall with an almost immediate ground collision which separated the engine and cartwheeled the airplane.

The Tempest lost its main landing gear during the cartwheeling before slamming onto its belly and sliding to a stop mostly intact. I taxied rapidly over to its resting place and we exited our plane. We jumped onto the wing and saw that the pilot was unconscious and still strapped in.

My student and I tried to locate the emergency canopy release handle and could not (we found out later that it had been removed due to cosmetics!). We tried in vain to break the canopy open and finally had to abandon our efforts because of smoke and flames erupted under the airplane. The cockpit filled with a dark grey smoke and the flames began to crawl around the wing's leading and trailing edges; my student and I exited the area by running toward the wingtip and jumping off upon reaching it. All we could do is watch as the poor pilot and once beautiful Tempest were consumed by fire. Very sad.

Here's what was revealed with a little investigation:
1. The pilot had flown the Tempest once before and had joked about its takeoff characteristics with his warbird buddies. It was his second warbird; his first was a beautiful Corsair. Habit patterns were in conflict with what was necessary to fly the Tempest.
2. The pilot refused to wear a hardhat because he felt the leather helmet was sufficient. Had he he may not have been knocked unconscious during the crash sequence and could have escaped or aided in his rescue.
3. The pilot did not like to perform takeoffs with his warbirds canopy open (for egress just in case). This is just plain dumb in my opinion.
4. The pilot had a habit of refusing dual instruction because he believed he was capable of mastering whatever airplane he desired to fly after reading the AFM/POH. Call it arrogance or ego... but he was eventually bit hard by this attitude.
5. The pilot disregarded SOP's as well as decommissioning safety items he felt were unnecessary. No idea how it was FAA certified for ops. Probably never seen by the FAA knowing how this fellow behaved.

The accident left a widow who also flew. She was the one who was injured in the PT-17 accident I mentioned earlier. This took place about a year after her husband died in the Tempest accident. After her recovery she sold all the airplanes, their successful business and moved to somewhere in AZ.

Not telling you folks this to be a downer... just to give you a little info on pilot behavior/attitude and details that could have been avoided had BOTH pilots been open to dual flight instruction and recurrency training. The wife was lucky... she survived her event and was either scared away from flying or realized she wasn't the type who should be flying.

A great post, the consequences of machines, adrenalin, bravado and a female audience can be serious. In my brief racing career at club level I saw 5 young men crash between the pits and the start line, all of them fffffing hilarious, but in different circumstances could have been serious.

 

[XBe02Drvr]

the consequences of machines, adrenalin, bravado and a female audience can be serious.

Hey, you left out the main ingredient: TESTOSTERONE!!

 

[pbehn]

Hey, you left out the main ingredient: TESTOSTERONE!!

Well testosterone is always there, put into the hyped up situation of a race circuit all the hormones combined can produce pure comedy. I guarantee if any of the guys were asked "why did you do that" they would answer "I don't know".

 

[gumbyk]

You just about hit the nail on the head with "unlearning" a habit-pattern. There are lessons to be learned with this unfortunate accident; read on if you wish.

I was next in line to take off behind the departing Tempest. My student and I drooled at its beauty and power-- it's another favorite airplane of mine. Our wonderment turned to shock as we saw that magnificent bird rapidly snaking and skipping down the runway until the pilot literally pulled it off the runway.... prematurely. This action lead to an immediate yaw/bank to the right and snap-stall with an almost immediate ground collision which separated the engine and cartwheeled the airplane.

The Tempest lost its main landing gear during the cartwheeling before slamming onto its belly and sliding to a stop mostly intact. I taxied rapidly over to its resting place and we exited our plane. We jumped onto the wing and saw that the pilot was unconscious and still strapped in.

My student and I tried to locate the emergency canopy release handle and could not (we found out later that it had been removed due to cosmetics!). We tried in vain to break the canopy open and finally had to abandon our efforts because of smoke and flames erupted under the airplane. The cockpit filled with a dark grey smoke and the flames began to crawl around the wing's leading and trailing edges; my student and I exited the area by running toward the wingtip and jumping off upon reaching it. All we could do is watch as the poor pilot and once beautiful Tempest were consumed by fire. Very sad.

Here's what was revealed with a little investigation:
1. The pilot had flown the Tempest once before and had joked about its takeoff characteristics with his warbird buddies. It was his second warbird; his first was a beautiful Corsair. Habit patterns were in conflict with what was necessary to fly the Tempest.
2. The pilot refused to wear a hardhat because he felt the leather helmet was sufficient. Had he he may not have been knocked unconscious during the crash sequence and could have escaped or aided in his rescue.
3. The pilot did not like to perform takeoffs with his warbirds canopy open (for egress just in case). This is just plain dumb in my opinion.
4. The pilot had a habit of refusing dual instruction because he believed he was capable of mastering whatever airplane he desired to fly after reading the AFM/POH. Call it arrogance or ego... but he was eventually bit hard by this attitude.
5. The pilot disregarded SOP's as well as decommissioning safety items he felt were unnecessary. No idea how it was FAA certified for ops. Probably never seen by the FAA knowing how this fellow behaved.

The accident left a widow who also flew. She was the one who was injured in the PT-17 accident I mentioned earlier. This took place about a year after her husband died in the Tempest accident. After her recovery she sold all the airplanes, their successful business and moved to somewhere in AZ.

Not telling you folks this to be a downer... just to give you a little info on pilot behavior/attitude and details that could have been avoided had BOTH pilots been open to dual flight instruction and recurrency training. The wife was lucky... she survived her event and was either scared away from flying or realized she wasn't the type who should be flying.

Sir Tim Wallace, who had a large warbird collection (including two spitfires) got caught out by this.
He had been doing a lot of flying in his MkIX, and then got into the MkXIV. Different rotation of propellers, and he wound the rudder trim the wrong way for take-off. It almost killed him as he couldn't put in enough rudder force to overcome the yawing motion on take-off.

 

[MIflyer]

Frank:

Thanks for that explanation. A s a matter of fact on Sunday I had a discussion about those same points with an aeronautical engineer/flight instructor who rents the hanger a couple of doors down from mine.

I also conducted some experiments with my own aircraft which is designed specifically to do away with the left-turning characteristic, but does not, entirely.

It is still not clear to me what was the biggest factor in the FW-190's stalling and spinning to the left while trying to follow the P-38 in the right spiral. The biggest factor may have been simply that the Germans had to lead the P-38 to hit it and thus needed extra right rudder.

Attached is a 1942 article on inward versus outward rotation on twin-engined airplanes. It is not as well written as I would like but does explain why outward turning propellers are preferred.

The XP-38 began with inward turning propellers but they found that it resulted in buffeting of the elevator and they switched to outward turning for the YP-38's and production models.

The P-82 started with outward turning propellers and they discovered that the airplane would not fly because the combination of the taildragger stance and the upward angled propwash stalling out the center wing. They switched the prop rotation and all was fine.

By the way, with the V-1710 the engine rotation could be switched with the replacement of a single gear; I don't know about the Merlin.

 

[wuzak]

As an observer, I've witnessed this: one fatal accident in a Tempest and one serious injury accident with a PT-17; and as a flight instructor surprised by my tail wheel students whom I was about to sign off for tail wheel flight operations.

Can I ask when and where that crash happened Frank?

 

[Frank G.]

In flight it produces a very pronunced braking effect. In the 1900, if we wanted to go down fast we would ease the power levers smoothly back to flight idle. As torque dropped almost to zero, the blades would flatten attempting to maintain governed RPM until they were against the low pitch stops and it was like having two barn doors out there. Certainly not negative thrust, but a huge braking effect, nonetheless. Done smoothly enough, and with well-timed trim adjustments, we could kill 30-50 KIAS and pick up a 1500-2000 FPM descent with a level deck angle and no change in prop noise. Pax seldom noticed.
Cheers,
Wes

Hi Wes,

It's called disc-drag and can be very useful as you alluded to. Mishandled and it can mess up the day.

Cheers,

Frank G.

 

[XBe02Drvr]

Mishandled and it can mess up the day.

Our colleagues on the 121 side of the company flying Fokker 27s envied us our propellers. They had no reverse thrust bearings in their Darts and couldn't use disc drag to any practical degree in flight. On the landing rollout they could use it gingerly, but had to be careful to maintain positive torque. Made for some dicy landings and/or rejected takeoffs in the wintertime. Those Dowty props had some weird feature where they could lock up against the low pitch stop, which would be fatal in flight.
Cheers,
Wes

 

[Frank G.]

Our colleagues on the 121 side of the company flying Fokker 27s envied us our propellers. They had no reverse thrust bearings in their Darts and couldn't use disc drag to any practical degree in flight. On the landing rollout they could use it gingerly, but had to be careful to maintain positive torque. Made for some dicy landings and/or rejected takeoffs in the wintertime. Those Dowty props had some weird feature where they could lock up against the low pitch stop, which would be fatal in flight.
Cheers,
Wes

Way back in the late 80's I worked a G-1 multiple fatality accident in Houston. Been a long time... my vague recall tells me it too had the good ole Dowty props, with its Christmas tree lights) that were somehow related to the cause. It wasn't my accident, I was one of the "worker-bees" assisting with the airframe reconstruction and documentation.

On the F-27, loved that airplane... never flew it, but liked its looks and sound. BTW, the Tempest accident I recounted earlier occurred at KUGN back in the 70's. Still can see that poor pilot slumped forward with the smoke entering the closed cockpit. On a different note, any idea how I can locate a flying example of an AVIA S-199?

As an aside-- Did some air testing with "zero-thrust," windmilling, propeller affect on pre-Vmc roll yaw performance. It's amazing how quickly a yaw-roll will occur in the opposite direction when one (in this case, the port engine) is windmilling and the left-hand yaw is beginning; when the operating engine is immediately retarded to idle. Hang on! Imagine that occurring close to the ground.

If you have any old ME-training manuals from back in the 80-90's, give a look at how stopping the beginning of a Vmc roll was supposed to be done. Believe that has since been changed due to a newly acquired awareness of immediate disc-drag affect and the potential consequences if in close proximity to the ground.

Enjoy your weekend,

Frank G.

 

[XBe02Drvr]

Way back in the late 80's I worked a G-1 multiple fatality accident in Houston. Been a long time... my vague recall tells me it too had the good ole Dowty props, with its Christmas tree lights) that were somehow related to the cause. It wasn't my accident, I was one of the "worker-bees" assisting with the airframe reconstruction and documentation.

On the F-27, loved that airplane... never flew it, but liked its looks and sound. BTW, the Tempest accident I recounted earlier occurred at KUGN back in the 70's. Still can see that poor pilot slumped forward with the smoke entering the closed cockpit. On a different note, any idea how I can locate a flying example of an AVIA S-199?

As an aside-- Did some air testing with "zero-thrust," windmilling, propeller affect on pre-Vmc roll yaw performance. It's amazing how quickly a yaw-roll will occur in the opposite direction when one (in this case, the port engine) is windmilling and the left-hand yaw is beginning; when the operating engine is immediately retarded to idle. Hang on! Imagine that occurring close to the ground.

If you have any old ME-training manuals from back in the 80-90's, give a look at how stopping the beginning of a Vmc roll was supposed to be done. Believe that has since been changed due to a newly acquired awareness of immediate disc-drag affect and the potential conse quences if in close proximity to the ground.

Enjoy your weekend,

Frank G.

I used to have the NTSB report on that G-1 crash. It seems most direct drive turpoprops such as Dart, Garrett, Allison, etc, need some sort of low pitch lock on shutdown to aid in starting. Only supposed to function on the ground, as in flight in a twin it would invariably be fatal. I'm told a P-3 or a Herc can survive if it's one of the inboards that goes rogue. All it takes is a sticky squat switch to ruin your whole day. I remember reading of a Dornier 2-28 (Africa, I think) that had a prop lock up when leveling from a sharp power-off descent and augered in.
My training manuals from the 60s and 70s said to retard both throttles and brace for impact if you lose an engine below VMC. (Why were you there in the first place??) I haven't been medically airworthy (eyes) since 1996, so haven't been paying attention. What's the current gospel on asymmetric thrust and survival? Thanks.
Cheers,
Wes

 

[swampyankee]

Hamilton props go off the governor to a fixed, low pitch when the power lever is pulled below flight idle. They do this to make aircraft handling on the ground easier, but going off the governor in flight will result in the prop windmilling, causing very high drag. Pushing the power lever forward right now may get the prop back on the governor before the engine's internals come apart — the power turbine shaft would fail or the power turbine would lose its blades — avoiding the crash. Most aircraft have a squat switch so prop stays on the governor in flight.

 

[BiffF15]

Wes,

The OV-10 and RC-26 (Metroliner) both used the direct drive Garret's. When shutting down we would put the the props "on the locks" to aid with the next start. You couldn't start a feathered prop as it turns during the start (always turning if motor is running).

Cheers,
Biff

 

[MIflyer]

Any of y'all ever see a C-130 start an engine with a bad starter by letting it windmill while going down the runway?

A 130 came into VAFB while I was there, offloaded a truck and then did the windmill start. They stopped with all engines running and next we heard the tower say, 'Yes, sir, you can taxi back if you wish. But you can just take off from there if you want to. You still have 8000 feet of runway left." They took off from where they had stopped.

 

[swampyankee]

Going back to propeller behavior.

The vector sum of the aircraft's velocity and the propeller's tangential velocity will cause a force perpendicular to the direction of motion if the aircraft's velocity vector is not parallel to the propeller's axis of rotation. The component is destabilizing if the propeller is ahead of the aircraft's center of gravity.

 

[XBe02Drvr]

The vector sum of the aircraft's velocity and the propeller's tangential velocity will cause a force perpendicular to the direction of motion if the aircraft's velocity vector is not parallel to the propeller's axis of rotation. The component is destabilizing if the propeller is ahead of the aircraft's center of gravity.

Sounds like engineer talk for: "Any amount of sideslip with a windmilling prop produces a tendency to the yaw-roll syndrome Frank G mentioned in an earlier post."
So here's an engineer question: Does that mean a twin engine pusher type a/c wouldn't be subject to yaw-roll syndrome?
Cheers,
Wes