P-38 MANEUVER Flap 8 Degrees?

[Randy1]

I am not sure how authoritative of a source Joe Baugher is considered on this forum on the P-38 variants but this is from the THE 456th FIGHTER squadron web site

The P-38F-15-LO introduced combat flaps which could be rapidly extended to 8 degrees during maneuvers to tighten the turning radius.

The single manual statement is the only source I can find saying 50%.  The introduction to the manual clearly states the information was not to be used for anything but information.   All specific technical information came from another source

From the all the technical information I can find 50% flap would be a poor choice for an enhanced maneuver setting.  The 8 degrees offered enhanced lift without a large increase in drag as is found in Fowler flaps at 50% deflection.

A fixed setting of 8 degrees would offered the pilot a do all setting without having to set the flaps by flap indicators.  This was especaily helpful since the flap handle was on the right side I would think.

[Ack-Ack]

Yeah, the P-38L manual I have also mentions 1/2 flaps for the Maneuver setting which is at odds with everything else I've read.  I've got some other manuals for the earlier Lightning series and I'm going to check to see if those say the same thing. 

ack-ack

[FLS]

I'm certain the 8 degrees is a mistake.  In addition to the pilot's manual, Lockheed also stated the maneuvering setting was a half extension of the flaps. That would be about 20 degrees.

A deflection of 8 degrees is a normal first notch combat setting. The P-51 and P-47 both consider the first notch the combat flap position but they aren't fowler flaps which also increase the wing area. The P-38 could set 8 degrees based on the cockpit gauge or indicator pin. Pulling the lever to the maneuver setting set the flaps to half extended. In the AH P-38 the best sustained turn rate and radius is 3 notches flaps, 2 notches can be the same rate with a larger radius from the higher speed.

[Randy1]

I went through every manual I could find and I do have some interesting notes although not conclusive.  In landing instructions they say set flaps to Maneuver setting.  In another part of the manual mention 50% flaps as if they were two different settings.  They table list 50% flaps but never mention Maneuver setting.

I can not find the Lockheed documentation giving the Maneuver setting as 50% or 8%.

The information I have found weighs heavily toward the maneuver setting be 8%.  Only on general information document says 50%.

[Ack-Ack]

I'm certain the 8 degrees is a mistake.  In addition to the pilot's manual, Lockheed also stated the maneuvering setting was a half extension of the flaps. That would be about 20 degrees.

A deflection of 8 degrees is a normal first notch combat setting. The P-51 and P-47 both consider the first notch the combat flap position but they aren't fowler flaps which also increase the wing area. The P-38 could set 8 degrees based on the cockpit gauge or indicator pin. Pulling the lever to the maneuver setting set the flaps to half extended. In the AH P-38 the best sustained turn rate and radius is 3 notches flaps, 2 notches can be the same rate with a larger radius from the higher speed.

It is rather confusing.  In Flying American Combat Aircraft of WWII: 1939-45, Volume 1; Volumes 1939-1945 (page 65), a P-38 pilot mentions, "While on top of the peel-up, in a vertical bank almost on our back, we chopped throttles and moved the flap handle into half-flap position (maneuver flaps)."

ack-ack

[bozon]

I'm certain the 8 degrees is a mistake.  In addition to the pilot's manual, Lockheed also stated the maneuvering setting was a half extension of the flaps. That would be about 20 degrees.

From this discussion it sounds to me like "1/2 flaps" means "somewhere in between" and not exactly 0.5 of the max flap angle. The term half is often used in this inaccurate way - like when people say "here, take the larger half".

Also, half travel of the flap is not half the deflection angle. The Fowlers first move backwards out of the wing and then deflects, so perhaps 10 degree deflection is about half the time to deflect full flaps and hence the "1/2" reference - the pilot hears the flaps motor working for about half the time. I still think that the "1/2" term is very liberally used to described a state between the min and the max.

[FLS]

I doubt they said half way and actually meant one quarter or one fifth.

The manual also states that half way is the max flap setting before you get more drag than lift.

[Puma44]

From the pilot's perspective, its a physical setting that produces a configuration determined by the design engineers, flight test pilots, etc.  The actual degree setting of the flaps is really not a big deal, as long as the flaps go to the configuration they are commanded to.  

[Randy1]

It is rather confusing.  In Flying American Combat Aircraft of WWII: 1939-45, Volume 1; Volumes 1939-1945 (page 65), a P-38 pilot mentions, "While on top of the peel-up, in a vertical bank almost on our back, we chopped throttles and moved the flap handle into half-flap position (maneuver flaps)."

ack-ack

AK AK, interesting.  We could be dealing with two possiable problems in trying to pin this down.  One, the terms "Maneuver Setting" and "Maneuver Flaps" are used interchangeably when they have different meanings.  The second is the original flap setting of 8 degrees may have been changed to 50%.

It is a good puzzle to solve.

[FLS]

The pilot manual also says you can use up to half flaps for a shorter takeoff run. This clearly indicates that half flaps is about 20 degrees not 8 degrees.

I wonder how the flap indicator pin was marked. The original cockpit gauge used before the maneuver setting was added was marked up, 1/4,1/2, 3/4, and down.

[Randy1]

The pilot manual also says you can use up to half flaps for a shorter takeoff run. This clearly indicates that half flaps is about 20 degrees not 8 degrees.

I wonder how the flap indicator pin was marked. The original cockpit gauge used before the maneuver setting was added was marked up, 1/4,1/2, 3/4, and down.

There is no question about 50% flaps being more than 8%.

Now I found a description on the term maneuvering flaps. The article said the quick acting Lockeed's fowler flaps of 3 seconds down and 4 seconds up were called maneuvering flaps. It appears Lockheed developed higher speed flap deployment for the P-38 and used the term maneuver flaps to describe them.

[Murdr]

 It's explicitly clear in TO-01-75F-1 that the maneuver position of the flap control lever will deploy the flaps 1/2 way.  In variants before there was a maneuver position, the pilot had to pull the lever to "OPEN", watch the flap indicator, and then push it to "CLOSED" when the gauge said it was at 1/2.  The addition of a maneuver position was merely a change in the hydraulics, to lessen the work load on the pilot.  This Tech Order manual covers F-4 through G variants, so it gives notes for both situations.

As far as the degrees of deflection, I have always taken what may be interpreted as a discrepancy to mean that the specific mechanics of the fowler flaps hydraulic throw range isn't linear with the degree of flap deflection.  You can see this in the diagram AKAK posted.  If you reference only the horizontal travel of the flap hinge point, the position marked "maneuver", is 1/2 way horizontally between "retracted" and "landing".

[Mongoose]

  Once upon a time, someone posted a link to AAF Manual 51-127-1, which is the Pilot Training Manual for the P-38.  It is a scanned document, so I can't copy and paste excerpts.  A quick google search found it available for download here:

https://drive.google.com/folderview?id=0Bw4FNWq6qRgqV251amlrdkdFcHc&usp=sharing

It talks about flaps starting on page 50.  According to this manual, there are four positions for the flap control lever:  Up, closed, maneu (short for maneuver), and down.  The instructions state that you use the Up and Down position to raise or lower the flaps, and move the lever to the closed position when you have the flaps at the desired position.  You can pull the lever straight to the maneuver position to move the flaps to the 50% down position for maneuvering in combat, or to prep for landing.  It does not say how many degrees this is.

[Murdr]

 Once upon a time, someone posted a link to AAF Manual 51-127-1

You can find that and a number of other manuals linked from the respective AHWiki page.  They are hosted on the trainers site.

[Murdr]

I maintain that the assumption of a 1:1 ratio between the range of motion of the hydraulics (which is what the gauge indicates) and degree of flap deflection is the cause of confusion.  The deflection is a function of where the flap assembly is at in the guide system.  The hydraulics merely move the flaps along the guides.  Can anyone see a mechanical truth in this diagram that excludes 50% of the hydraulic throw also being 8 degrees?