Contra rotating Propellers

[FLYBOYJ]

I think the problem we have here is the fact that there are no other aircraft (that I am aware of) that have two outward turning engines as the P-38 does.
In most aircraft the engines all turn either clockwise or counter-clockwise; some aircraft have counter-rotating engines that make things easier for the pilot to handle in the case of an engine failure (inward turning). The "critical engine" definition becomes quite easy.

The P-38 is unique (I believe) in that in the case of failure with either engine you have a serious control issue, particularly at lower airspeeds. The fact that the control problems are similar no matter which fails doesn't change that fact. The reduction in power tends to reinforce the point that there isn't enough stabilizer or rudder to overcome the asymmetric thrust the engines can develop. That alone could make either engine critical.

Agree to a point but as stated folks like Tony Levier showed that the aircraft indeed could be handled at the most extreme conditions with one engine out if the pilot knew what he was doing.

You have mentioned specific wording in the FAR's as relevant, I would suggest that hanging your hat on that particular hook doesn't cut it because in regulations as well as any other documents every specific instance or aircraft will not be called out, you have to remember you own words, " The P-38 was not built under part 23.".

That's correct so with that said does the definition of a critical engine in FAR 1 apply? Again I vew it as having the glass "half full or half empty."

 

[FLYBOYJ]

I work at the USAFA and work with the 98th FTS. They operate Twin Otters. Many of them have tons of twin time and some are test pilot school grads. I asked 6 of them "if a twin engine aircraft has the same engine out performance characteristics regardless of the engine you shut down or loose, does the aircraft still have a critical engine?"

3 said yes, 3 said no.

I asked my father in law, a retired USAF LtCol, former test pilot and retired United Airlines Captain. Without pause he said "no."

His explanation was based on a training mentality stating that "the plane will fly just as crummy on the right engine as the left, so why confuse the issue"?

Not my opinions. I'll field more folks for their opinions.

 

[ccheese]

I'm not into the technical stuff like Joe, but I have flown in quite a few twins (B-26, B-25, A-20, R4D. P2V and the TF. Without exception, I've been along when an engine was shut down for whatever reason. I've talked to the pilots, and except for the R4D (C-47) the guys up front had their hands full of airplane. I remember the B-26 jockey saying both the pilot and the co-pilot had their feet on the rudder pedal. It can't be fun !

I also flew in the C-119, and fortunately never lost an engine. I do not think the C-119 will fly on one engine. If it will, I don't want to be on board.

Charles

 

[FLYBOYJ]

I also flew in the C-119, and fortunately never lost an engine. I do not think the C-119 will fly on one engine. If it will, I don't want to be on board.

Charles

A engine out on a C-119 would be a scary thing indeed!

I got more of an explanation out of my father in law - In his opinion when assuming you have a twin with a critical engine, there is a comparison made in performance between the right and left engine. As he simply put it if the aircraft flies the same regardless of which engine is out then how can you have a critical engine with no performance comparison?

 

[Bruce R.]

Agree to a point but as stated folks like Tony Levier showed that the aircraft indeed could be handled at the most extreme conditions with one engine out if the pilot knew what he was doing.

Test pilots like Tony Levier, Chuck Yeager, Boone Guyton, and Scott Crossfield, to name just a few are and were exceptional people with exceptional skills, the fact that they could handle a plane with "different" characteristics isn't surprising, nor should it be. I knew Scott Crossfield, and I saw what Bob Hoover could do with an F-100 when Air Force pilots were running off the runways at Clark AFB with burned up brakes and drag chutes deployed early. Guys with those skills are not close to average pilots by any means.

That's correct so with that said does the definition of a critical engine in FAR 1 apply? Again I view it as having the glass "half full or half empty."

Actually, yes it does. The FAA is the governing body on all things related to aircraft since its inception. They have stayed out of the military arena because the pilot training and aircraft requirements are different from civilian needs. Since there are no longer any P-38's in military service, and all remaining aircraft are owned by civilians, they (P-38's) are now under FAA jurisdiction, so Part 23 as well as any and all other regs. also have full weight of law.

 

[FLYBOYJ]

Test pilots like Tony Levier, Chuck Yeager, Boone Guyton, and Scott Crossfield, to name just a few are and were exceptional people with exceptional skills, the fact that they could handle a plane with "different" characteristics isn't surprising, nor should it be. I knew Scott Crossfield, and I saw what Bob Hoover could do with an F-100 when Air Force pilots were running off the runways at Clark AFB with burned up brakes and drag chutes deployed early. Guys with those skills are not close to average pilots by any means.

Agree - but at the same time you had your Bongs, McGuires, Lynchs' and Johnsons' who were able to do the same things with the p-38, but agree, those type of P-38 pilots were the exception rather than the rule

Actually, yes it does. The FAA is the governing body on all things related to aircraft since its inception. They have stayed out of the military arena because the pilot training and aircraft requirements are different from civilian needs. Since there are no longer any P-38's in military service, and all remaining aircraft are owned by civilians, they (P-38's) are now under FAA jurisdiction, so Part 23 as well as any and all other regs. also have full weight of law.

FAR 23 would apply to a type certificated aircraft as it would be deemed "airworthy" after certification and required inspections, the first line of FAR 23 specifies applicability - "(a) This part prescribes airworthiness standards for the issue of type certificates, and changes to those certificates, for airplanes in the normal, utility, acrobatic, and commuter categories."

Former military aircraft like the P-38 that doesn't have a TCDS would be granted an "experimental" air worthiness certificate (you probably know all this) under FAR 21.191, 193 and 195. An aircraft lacking a TCDS and given an "experimental" airworthiness certificate is allowed to fly based on the issuance of a program letter (where its specified under what type of experimental catagory the aircraft will fly in, Exhibition, R&D, Racing, demostration of compliance, amature, kit built and certain training) and a maintenance program. The FSDO and in some cases MIDO will determine if the aircraft is "safe for flight" and it's operating area based on those documents. Additionally it is within those documents where operational flight parameters are spelled out (usually a standard flight manual developed by the manufacturer and any supplements for additional equipment, ie. radios, GPSs, etc). In the end an "Experimental" aircraft that is a former warbird will never be in compliance with FAR 23 as it was never certificated under FAR 23 requirements, in fact an experimental aircraft of this type could never be signed off as "airworthy" - instead the term "safe for flight or operation" is the nomenclature used to issue airworthiness certificates and to sign off condition inspections. Additionally there are FAR 23 requirements where an aircraft like a P-38 could never meet (placement of instruments, proper markings, landing gear and flap handle configuration and location, etc. just to name a few)


I've applied for and gotten about 20 experimental airworthiness certificates for various warbaird owners that included recips, jets and helicopters. I know this process better than I sometimes wish to!

 

[HoHun]

Hi Flyboyj,

>Again if the failure of either engine give you the same end result, how can you have a "critical engine?" Or as stated by Bruce, both engines are critical, but then again you don't have one that brings greater adversity to the situation!

From the FAR perspective, I'd say that "critical engine" is just a definition device to arrive at a conservative Vmc figure. If both single-engine flight variants arrive at the same figure, there is no critical engine from that point of view.

However, you could apply FAR criteria twice to a twin and determine "Vml" and "Vmr" (I made these up - minimum single engine speed on the left respectively right engine). For a P-38 with conventional engines (I believe the British export variant didn't have counter-rotating propellers), Vml and Vmr would be different. For the US variants, they would be identical, coinceding with the historical Vmc - and match the higher of the two British figures!

That's why one could say that both of the P-38's engines were "critical" ...it's not true in the sense of the FAA definition, but you really end up with the "worse case" minimum single-engine speed figure no matter which engine fails.

If you think it through, the direction in which the *stopped* engine used to turn determines if the engine that is still turning is considered to be critical or not!

If a British Lightning would fly alongside a US Lightning, both having their left engine stopped, you'd have two identical aircraft with the right engine turning in the same direction. The British one would be flying on a critical engine and the US one not - but the pilots would find their handling to be completely identical ...

I think it's a healthy reaction to consider this a bit confusing

Regards,

Henning (HoHun)

 

[davparlr]

I work at the USAFA and work with the 98th FTS. They operate Twin Otters.

Twin Otters don't fly, they just taxi in the air!

The only twin engine aircraft I have flown were basically centerline thrust, T-37 and T-38, but for non centerline thrust twins, I think procedures would be for worst case and applied to either engine out. Good basic aircraft control should suffice. You don't want average pilots thinking too hard in stress.

 

[pbfoot]

Twin Otters don't fly, they just taxi in the air!

The only twin engine aircraft I have flown were basically centerline thrust, T-37 and T-38, but for non centerline thrust twins, I think procedures would be for worst case and applied to either engine out. Good basic aircraft control should suffice. You don't want average pilots thinking too hard in stress.

They are in production again after 20 years and with possibly the Beaver and Otter to follow on. Even the US Army has ordered them
Viking Air - 03/18/2008 - Viking Lands Three Orders for New Twin Otter Series 400 Aircraft from U.S. Army

 

[FLYBOYJ]

You don't want average pilots thinking too hard in stress.

And I think that's where the thinking was to say that the P-38 had no critical engine.

 

[FLYBOYJ]

Hi Flyboyj,

>Again if the failure of either engine give you the same end result, how can you have a "critical engine?" Or as stated by Bruce, both engines are critical, but then again you don't have one that brings greater adversity to the situation!

From the FAR perspective, I'd say that "critical engine" is just a definition device to arrive at a conservative Vmc figure. If both single-engine flight variants arrive at the same figure, there is no critical engine from that point of view.

However, you could apply FAR criteria twice to a twin and determine "Vml" and "Vmr" (I made these up - minimum single engine speed on the left respectively right engine). For a P-38 with conventional engines (I believe the British export variant didn't have counter-rotating propellers), Vml and Vmr would be different. For the US variants, they would be identical, coinceding with the historical Vmc - and match the higher of the two British figures!

That's why one could say that both of the P-38's engines were "critical" ...it's not true in the sense of the FAA definition, but you really end up with the "worse case" minimum single-engine speed figure no matter which engine fails.

If you think it through, the direction in which the *stopped* engine used to turn determines if the engine that is still turning is considered to be critical or not!

If a British Lightning would fly alongside a US Lightning, both having their left engine stopped, you'd have two identical aircraft with the right engine turning in the same direction. The British one would be flying on a critical engine and the US one not - but the pilots would find their handling to be completely identical ...

I think it's a healthy reaction to consider this a bit confusing

Regards,

Henning (HoHun)

Great perspective, your last comment nails it!

 

[mkloby]

I work at the USAFA and work with the 98th FTS. They operate Twin Otters. Many of them have tons of twin time and some are test pilot school grads. I asked 6 of them "if a twin engine aircraft has the same engine out performance characteristics regardless of the engine you shut down or loose, does the aircraft still have a critical engine?"

3 said yes, 3 said no.

I asked my father in law, a retired USAF LtCol, former test pilot and retired United Airlines Captain. Without pause he said "no."

His explanation was based on a training mentality stating that "the plane will fly just as crummy on the right engine as the left, so why confuse the issue"?

Not my opinions. I'll field more folks for their opinions.

No degredation in handling characteristics w/ either eng out is true, since that is the basis for determining which would be a critical engine. I would answer no also.

 

[FLYBOYJ]

No degredation in handling characteristics w/ either eng out is true, since that is the basis for determining which would be a critical engine. I would answer no also.

Thanks for the input - maybe you could field this questions to some of your fellow "devil-dogs."

 

[davparlr]

They are in production again after 20 years and with possibly the Beaver and Otter to follow on. Even the US Army has ordered them
Viking Air - 03/18/2008 - Viking Lands Three Orders for New Twin Otter Series 400 Aircraft from U.S. Army

Hard to keep a good plane down!

 

[Wingscrubber]

Machineshoptom, what kind of engine is that? Looks like a Tupolev bear engine...