« previous next »
Pages: [1] 2 3 4 ... 10   Go Down

Author Topic: P-38 dive flaps produce no drag  (Read 14233 times)

Offline GScholz

  • Plutonium Member
  • *******
  • Posts: 8910
P-38 dive flaps produce no drag
« on: March 10, 2014, 08:37:20 PM »
Was very surprised to test and find that the P-38's dive recovery flaps do not produce drag. Top level speed is not affected by deploying these flaps.



I'm pretty sure something that big and uncompromisingly flat is going to produce a lot of drag. Right?
Logged
"With the first link, the chain is forged. The first speech censored, the first thought forbidden, the first freedom denied, chains us all irrevocably."

Offline USRanger

  • AvA Staff Member
  • Plutonium Member
  • *******
  • Posts: 10325
      • BoP Home
Re: P-38 dive flaps produce no drag
« Reply #1 on: March 10, 2014, 10:57:10 PM »
Ooh good find! :aok
Logged
Axis vs Allies Staff Member
☩ JG11 Sonderstaffel ☩
Flying 'Black[Death] 10' ☩JG11☩

Only the Proud, Only the Strong Ne Desit Virtus

Offline CASHEW

  • Nickel Member
  • ***
  • Posts: 371
Re: P-38 dive flaps produce no drag
« Reply #2 on: March 10, 2014, 11:55:20 PM »
Yeah hitech will fix this in the next millennium.
Logged
Peanut1 in game.

Offline Ack-Ack

  • Radioactive Member
  • *******
  • Posts: 25260
      • FlameWarriors
Re: P-38 dive flaps produce no drag
« Reply #3 on: March 11, 2014, 12:28:25 AM »
It wouldn't effect top speed like a dive brake would. 

ack-ack

Logged
"If Jesus came back as an airplane, he would be a P-38." - WW2 P-38 pilot
Elite Top Aces +1 Mexican Official Squadron Song

Offline GScholz

  • Plutonium Member
  • *******
  • Posts: 8910
Re: P-38 dive flaps produce no drag
« Reply #4 on: March 11, 2014, 08:49:04 AM »
It must produce drag, thus it must affect top speed. They couldn't make a bomb pylon drag free, but what is in effect an under-wing spoiler was magically drag free?
Logged
"With the first link, the chain is forged. The first speech censored, the first thought forbidden, the first freedom denied, chains us all irrevocably."

Offline Randy1

  • Platinum Member
  • ******
  • Posts: 4232
Re: P-38 dive flaps produce no drag
« Reply #5 on: March 11, 2014, 03:04:50 PM »
Quote from: Ack-Ack on March 11, 2014, 12:28:25 AM
It wouldn't effect top speed like a dive brake would. 

ack-ack



Not like a dive brake yes but it would effect top speed.  Alter the skin shape and you alter the drag coefficient one way or the other albeit ever so slight.  It could be only be one tenth of an MPH or it might be two or three.  That we don't know until some one finds the missing piece of information like a performance retest of the J with and without the device.  Till then, no bases for a change.
Logged

Offline GScholz

  • Plutonium Member
  • *******
  • Posts: 8910
Re: P-38 dive flaps produce no drag
« Reply #6 on: March 11, 2014, 03:57:16 PM »
More like several tens of mph, at least. A single center line ord pylon on a WWII fighter reduces top level speed by 3-5 mph, or more.
Logged
"With the first link, the chain is forged. The first speech censored, the first thought forbidden, the first freedom denied, chains us all irrevocably."

Offline Randy1

  • Platinum Member
  • ******
  • Posts: 4232
Re: P-38 dive flaps produce no drag
« Reply #7 on: March 11, 2014, 05:44:23 PM »
Quote from: GScholz on March 11, 2014, 03:57:16 PM
More like several tens of mph, at least. A single center line ord pylon on a WWII fighter reduces top level speed by 3-5 mph, or more.

Even if that were so, the device is to be used in a dive, not normal level flight.  In a dive the max speed is only limited by man and machine.   Still a mute point.
Logged

Offline FLS

  • AH Training Corps
  • Plutonium Member
  • *******
  • Posts: 11618
      • Trainer's Website
Re: P-38 dive flaps produce no drag
« Reply #8 on: March 11, 2014, 06:22:55 PM »
Quote from: GScholz on March 11, 2014, 08:49:04 AM
It must produce drag, thus it must affect top speed. They couldn't make a bomb pylon drag free, but what is in effect an under-wing spoiler was magically drag free?

The dive flap is extended to 35 degrees per the pilot manual. It's not 90 degrees like a spoiler. I don't know what it adds to the drag coefficient.
Logged

Offline GScholz

  • Plutonium Member
  • *******
  • Posts: 8910
Re: P-38 dive flaps produce no drag
« Reply #9 on: March 11, 2014, 07:03:37 PM »
An excerpt from the P-38L's pilot manual was posted in the aircraft forum:

"The dive recovery flaps which are installed under the wings between the booms and the ailerons, restore the lift to this portion of the wing and thus cause the uncontrollable nose heaviness to occur at a higher speed. The flaps also add some drag to the airplane, which in conjunction with the higher allowable dive speed, permits safe dives at a much steeper diving angle. The dive recovery flaps should be extended before starting the dive or immediately after the dive has started before a buffeting speed has been reached. If the airplane is buffeting before the dive recovery flaps are extended, the buffeting will momentarily increase and then diminish. With these flaps extended, the nose heaviness is definitely reduced but the diving speed should never be allowed to exceed the placard by more than 15 or 20 mph. With the dive recovery flaps extended before entering the dive, angles of dive up to 45° may be safely accomplished. Without dive recovery flaps extended, the maximum angle for extended dives is 15°."

Note that the flaps do not allow for an increase in dive speed of more than "15 or 20 mph" while allowing an increase in dive angle of 30 degrees (from 15 degrees without flaps to 45 degrees with flaps). That takes drag... and a lot of it.

Not 90 degree dive bomber speed brake drag of course, but 45 degree dive bomber speed brake drag...



So... All the data needed is right there. With the dive flaps extended the P-38L should be able to safely dive at 45 degrees, but the top dive speed should only be 15 to 20 mph more than in a 15 degree dive without dive flaps.
« Last Edit: March 11, 2014, 07:09:52 PM by GScholz »
Logged
"With the first link, the chain is forged. The first speech censored, the first thought forbidden, the first freedom denied, chains us all irrevocably."

Offline FLS

  • AH Training Corps
  • Plutonium Member
  • *******
  • Posts: 11618
      • Trainer's Website
Re: P-38 dive flaps produce no drag
« Reply #10 on: March 12, 2014, 01:28:48 AM »
The dive flap worked by reducing buffeting and preventing the center of pressure on the wing from moving back and tucking the nose down. This is a separate effect from the drag it may have caused and can't be used to infer the difference in drag. That speed difference was just in controlability at higher speeds. I have a P-38 pilot manual AAF 51-171-1 that doesn't mention drag at all when describing the dive flaps so it likely wasn't significant. It does look like there should be a little drag and maybe a trim change but I haven't seen any figures on it.
Logged

Offline BnZs

  • Platinum Member
  • ******
  • Posts: 4207
Re: P-38 dive flaps produce no drag
« Reply #11 on: March 12, 2014, 01:37:57 AM »
You do realize introducing some measure of drag to the dive flaps would be to the advantage of P-38 pilots right? Anyway, rather surprised they don't induce some drag. You tested this offline?
Logged
"Crikey, sir. I'm looking forward to today. Up diddly up, down diddly down, whoops, poop, twiddly dee - decent scrap with the fiendish Red Baron - bit of a jolly old crash landing behind enemy lines - capture, torture, escape, and then back home in time for tea and medals."

Offline GScholz

  • Plutonium Member
  • *******
  • Posts: 8910
Re: P-38 dive flaps produce no drag
« Reply #12 on: March 12, 2014, 01:48:15 AM »
Yes I tested it offline. I don't care who it is or isn't an advantage to. Why would you even think in those terms in a bug report thread?  :huh

Would you actually prefer a bug to remain in the game if it is to your advantage?
Logged
"With the first link, the chain is forged. The first speech censored, the first thought forbidden, the first freedom denied, chains us all irrevocably."

Offline BnZs

  • Platinum Member
  • ******
  • Posts: 4207
Re: P-38 dive flaps produce no drag
« Reply #13 on: March 12, 2014, 01:52:18 AM »
Quote from: GScholz on March 12, 2014, 01:48:15 AM
Yes I tested it offline. I don't care who it is or isn't an advantage to. Why would you even think in those terms in a bug report thread?  :huh

Would you actually prefer a bug to remain in the game if it is to your advantage?

No. Just pointing out that  deceleration device is quite useful in ACM. It seems odd to me that HTC has overlooked this bit.
Logged
"Crikey, sir. I'm looking forward to today. Up diddly up, down diddly down, whoops, poop, twiddly dee - decent scrap with the fiendish Red Baron - bit of a jolly old crash landing behind enemy lines - capture, torture, escape, and then back home in time for tea and medals."

Offline nrshida

  • Plutonium Member
  • *******
  • Posts: 8632
Re: P-38 dive flaps produce no drag
« Reply #14 on: March 12, 2014, 02:05:32 AM »
Quote from: GScholz on March 12, 2014, 01:48:15 AM
Would you actually prefer a bug to remain in the game if it is to your advantage?

Not exactly unprecedented.



Logged
"If man were meant to fly, he'd have been given an MS Sidewinder"
Pages: [1] 2 3 4 ... 10   Go Up
« previous next »