Extra drag from open bomb bay doors

[fastmongrel]

How much speed was lost (if any) when a bomber opened its doors on the run to a target. I was specifically thinking of RAF heavies but interested in any figures. Also did the doors opening cause any turbulence that could upset a bomb aimer and was there a set time before the drop that the doors had to be opened.

 

[FLYBOYJ]

I don't know about turbulence but I do know that aircraft with bomb bay doors usually had a speed restriction when they were opened. For example I do believe the Mossie was limited to 305 knots with the bomb bays opened.

 

[wuzak]

I don't know about turbulence but I do know that aircraft with bomb bay doors usually had a speed restriction when they were opened. For example I do believe the Mossie was limited to 305 knots with the bomb bays opened.

Is that IAS or TAS?

It must be TAS, because 305kt IAS at high altitude would still be pretty quick.

Still, 305kt ~ 350mph, so just about a Mosquito's fast cruise speed.

 

[bobbysocks]

like flyboyj i would have figured there was a "never exceed" speed for deploying the bombay doors but i cant find it ( at least for the B24 ). i even looked in the B24 manual in this thread:

http://www.ww2aircraft.net/forum/other-mechanical-systems-tech/b-24d-pilot-manual-6802.html

it gives speed restrictions for weight, lowering gear, flaps, engaging auto pilot, etc...but says not one word about BB doors. i even checked in the emergency procedures....figuring with a full load the ac couldnt exceed the speed but empty and in trouble it might. nothing in the door operation/emergency procedures either. i am sure it knocked down the AS but might have to ask a former pilot for the answer to that....

 

[drgondog]

The B-24 was different from a B-17 or 26 or 29. The roller doors retracted, rather than float in the freestream and had much less drag.

 

[bobbysocks]

Ahhh ok. if i have time i will see if i can find it in FM for one of those....it struck me as odd there was a speed restriction.

 

[drgondog]

Well - it probably didn't occur to anybody in most USAAF bombers that bombs should be dropped while in a dive.. so bomb bay doors were used in B-17/24/25/26/29 and A-20 in level flight..

 

[FLYBOYJ]

Is that IAS or TAS?

It must be TAS, because 305kt IAS at high altitude would still be pretty quick.

Still, 305kt ~ 350mph, so just about a Mosquito's fast cruise speed.

I believe it's indicated. It's out of a flight manual for FB6 para 52 shows all the limitations.
http://www.zenoswarbirdvideos.com/Images/Mosquito/MosquitoFB6Manual.pdf

 

[Shortround6]

I would think that most restrictions would be indicated air speed. You don't want the pilot trying to do mathematics in his head trying to figure out if he is at the right speed to open the bombbay. Or scribbling figures on a note pad strapped to his thigh while on the bomb run

 

[drgondog]

IAS for US. Dive placards were expressed IAS vs altitude and reflective of Q loads.. 305 kts IAS for a Mossie is way up there at 25K as far as Q loading on the doors

 

[wuzak]

IAS for US. Dive placards were expressed IAS vs altitude and reflective of Q loads.. 305 kts IAS for a Mossie is way up there at 25K as far as Q loading on the doors

I would think that 305kts IAS @ 20,000ft would be probably faster than the Mosquito FB.VI could go on the level.

 

[pattle]

Some older planes such as the Bristol Blenheim had bomb bay doors that were held shut by bungee and would open by the weight of the bombs on them, this sounds very unsafe and apparently the small delay caused by the bombs passing through the bomb bay doors could effect their aim.

 

[bobbysocks]

the only thing i can find are the do not exceed glide and climb angles based on differing weight bombs and bomb loads ( B17)...no VBBO. i do find that odd.

 

[Balljoint]

Some older planes such as the Bristol Blenheim had bomb bay doors that were held shut by bungee and would open by the weight of the bombs on them, this sounds very unsafe and apparently the small delay caused by the bombs passing through the bomb bay doors could effect their aim.

Some of the newer planes would ice up the bomb bay doors and drop the bombs through the doors.