Corsair as Dive Bomber?

[Freebird]

I saw this mentioned on a different forum - the Corsair's landing gear extended as dive brakes?
Was this really a viable option?
And was this intended by design, or battlefield improvisation?
Was it commonly done?

F4U using gear as dive brakes

 

[bobbysocks]

I have heard of fighter pilots start to drop gear for various reasons... but you would have to be very careful doing this as if you exceed V LE then you could do a lot of damage to your plane.

 

[GrauGeist]

In the F4U-4 pilot's manual AN 01-45HB-1, on pages 13 - 14, section 4, is titled:
(4) DIVE BRAKE CONTROL - (a) The dive brake control is located on the left hand shelf. To extend the dive brake, move the landing gear control into the "DOWN" position of the dive brake slot; this extends the main landing gear only, leaving the tail wheel retracted. To retract the dive brake, move the control to "UP".

It refers the reader to "figure 14", which is on page 17, showing the airframe flaps and landing gear hydraulic system, including the dive brake system and controls (with control panel inset).

 

[wuzak]

At what angle could the Corsair dive with the dive brake control?

 

[Freebird]

In the F4U-4 pilot's manual AN 01-45HB-1, on pages 13 - 14, section 4, is titled:
(4) DIVE BRAKE CONTROL - (a) The dive brake control is located on the left hand shelf. To extend the dive brake, move the landing gear control into the "DOWN" position of the dive brake slot; this extends the main landing gear only, leaving the tail wheel retracted. To retract the dive brake, move the control to "UP".

It refers the reader to "figure 14", which is on page 17, showing the airframe flaps and landing gear hydraulic system, including the dive brake system and controls (with control panel inset).

So this was a purpose designed system then?

Was this the WWII manual? Or later?

 

[GrauGeist]

Yes, it was a purpose-built feature and the initial date of issue for this manual was 1 October 1944 with later revisions.

I'll see about getting you some page views when I'm on the computer and not this ipad.

 

[Shortround6]

The Manual for the F4U-1, FG-1, F3A-1 (Goodyear and Brewster built versions) mentions the airbrake and states the airbrake will not fully extend and lock at speeds over over 260kts and should not be retracted at speeds over 350knts.
Aside from being mentioned in the dive checklist and the above restrictions the manual has a very similar passage to that given by GrauGeist for the F4U-4.

The pilot's manuals are about basic flying and restrictions for a type of aircraft. Actual tactics/procedures for different operations would be in a different manual/publication. For example there are NO suggestions/hints/tips for air to air combat in fighter manuals.

 

[Greyman]

For what it's worth - British Pilot's Notes:

(i) Maximum speeds
Lowering undercarriage (normal) .. 200 knots IAS

(iii) Dive bombing
Maximum speed (undercarriage up) .. 375 knots IAS
Maximum speed for lowering undercarriage (dive brakes) .. 250 knots IAS
Maximum speed undercarriage down .. 350 knots IAS

(vi) Bombs
Maximum speed when carrying bombs .. 375 knots IAS
Maximum speed when releasing bombs .. 300 knots IAS
Accelerating and arresting are permissible, but the angle of dive when releasing bombs must not exceed 60 degrees. Salvo release is not permitted.

 

[drgondog]

Often wrong but rarely uncertain - I would doubt that any analysis of 'performance considerations of lowered landing gear' was considered in preliminary design. I suspect that the limits were brought to screeching attention when a wing failure occurred due to lowering gear at high speed.

This example specifically occurred due to P-51B wing failures when the wheel/gear uplock failed in high G pullouts, the gear crashed through the wheel cover, caught a 400+kts blast of dynamic pressure and yanked a wing off.

 

[michaelmaltby]

The Saab B-17 was engineered around the lowered landing gear strategy

 

[Shortround6]

The feature of using the landing gear on the F4U as a dive brake may or may not have been in the initial design. It may have been added among the 800 or so modifications between the prototype and the first production models. The F4U being the first Navy plane to be exempt from the terminal velocity dive test. The plane/s the Navy purchased (at least prototypes) had to make a dive of such length/duration that the plane reached a speed at which it would simply go no faster due to drag. With the Corsair the initial dives took up so much altitude and required such severe pullouts (and were running into comprehensibility problems) that the Navy canceled the requirement.
Perhaps the lowered landing gear air brake was added at this time help restrict dive speeds in general. The idea that the landing gear and doors would act as a dive brake for dive bombing in a way similar to true dive bombers takes a bit of swallowing.

Dive brakes on SBD

SBC Helldiver dive brakes.

The F4U landing gear would certainly help but I doubt it could allow dives of thousands of feet near 60 degrees.

 

[RCAFson]

For what it's worth - British Pilot's Notes:

Accelerating and arresting are permissible, but the angle of dive when releasing bombs must not exceed 60 degrees. Salvo release is not permitted.

This what my F4U manual AN 01-45HA-1 states:

DIVE BRAKE CONTROL-The dive brake con-
trol may be operated at any speed within the normal air-
plane restrictions in Model F4U-l airplanes number 82278
and subsequent and Model FG-l airplanes number 76196
and subsequent. When the dive brake control is oper-
ated at speeds greater than 260 knots, the wheels will
trail instead of extending fully and locking but are never-
theless effective as a dive brake, For all other Model
F4U-l, FG-l, and F3A-1 airplanes, the limiting speed for
operation of the dive brake control to extend or trail the
landing gear is 380 knots but is unrestricted (within the
normal airplane restrictions) with the landing gear fully
extended and locked down.

I suspect that the 60 deg drop limitation was due to the fact that all bombs were carried very near the centre-line and consequently they could contact the prop at very steep dive angles. However, I can't find anything about that in the above manual.

 

[stona]

T

I suspect that the 60 deg drop limitation was due to the fact that all bombs were carried very near the centre-line and consequently they could contact the prop at very steep dive angles. However, I can't find anything about that in the above manual.

Because they wouldn't hit the propeller. Both the the USAAF and the USN established this independently, the USAAF using 'vertical' dives with a P-47. I'd have to look up which aircraft the USN used, but the results were discussed at the Patuxent River fighter conference and I posted the relevant section in another thread sometime ago.
'Vertical' dives, at least in USAAF parlance, seem to refer to any dive at an angle of 70 degrees or more...not necessarily literally vertical.
Cheers
Steve

 

[tomo pauk]

...
(and were running into comprehensibility problems)
...

Happened to me many times

 

[stona]

I have found the relevant page in the 8th AF history.

Cheers

Steve

 

[RCAFson]

Because they wouldn't hit the propeller. Both the the USAAF and the USN established this independently, the USAAF using 'vertical' dives with a P-47. I'd have to look up which aircraft the USN used, but the results were discussed at the Patuxent River fighter conference and I posted the relevant section in another thread sometime ago.
'Vertical' dives, at least in USAAF parlance, seem to refer to any dive at an angle of 70 degrees or more...not necessarily literally vertical.
Cheers
Steve

I'd be curious to see what the USN tests showed.

You can see here that the P-47 and F4U have very different centre line prop/bomb geometry:
File:Republic P-47N 3-side drawings.PNG - Wikipedia
https://upload.wikimedia.org/wikipe...air_Standard_Aircraft_Characterisics_1953.PNG

note how the P-47 prop circle just covers the DT with the prop tip while that of the F4U covers the DT at the mid point of the prop.

 

[stona]

I'd be curious to see what the USN tests showed..

Essentially that the aircraft separates from and accelerates away from the bomb.

pp156/7 of my edition of the 'Report of Joint Fighter Conference'.

Commander Monroe:
"Our fighters are authorized to dive up to 85 degrees. Of course they have no displacing gear. Careful investigation down here shows absolutely no danger of the bomb hitting the propeller. At least the airplane and the bomb keep their relative pressures fore and aft, and the bomb drops away from the airplane, which was a great relief to everybody."

This agrees broadly with what the USAAF had also discovered.

Whether 'our fighters' includes the F4U I can't say for sure. The date of the conference was 16th - 23rd October 1944, so it had been in service for some time.

In the interest of balance, I have read somewhere (can't remember where) that Douglas were developing a bomb displacement system powered by a cartridge, and an automatic pull out system, both designed to throw a bomb clear of an aircraft propeller. I don't know which aircraft were involved, and as far as I know such a system never saw service. I would happily be corrected, US aircraft are not really my forte

Cheers

Steve

 

[Milosh]

edit ; wrong thread
Thanks GG for the fix

 

[GrauGeist]

Somewhere after the "steady 400-500 boat" portion of your post, the strike command was used, this is an S contained in brackets [ S ]

Go into the editor, select "plain text editor" (little wrench in the upper right of the tool bar) and look for that command in your post. You can't see the BBS commands in rich text.

 

[Dana Bell]

Hi Guys,

The landing gear/speed brake combination was part of the initial design of the Corsair, derived from the same feature on the Vindicator. Vought developed separate speed brakes for the SB2U, but the Navy preferred to save the weight and use the landing gear for the purpose. Remember that early Corsairs carried no centerline bomb racks, using only two outboard wing racks for light bombs (part of the Navy's demand that all fighters be capable of suppressing shipboard anti-aircraft fire).

Cheers,


Dana