SE5 armament

[mik]

I have never come across any acounts of pilots unable to hit what they shot at with SE5a guns. The Vickers seem to be set at about 5 degrees above line of flight. No one has been able to explain to me why this was done. I read in one of my books (can't remember which one) that the guns were set to converge at about 50yards in front of the aircraft.

[mik]

I don't remember where I got 50 yards from. But this is from "Mount of Aces"

On 26 August, a query, originating with 60 Squadron, was raised regarding the aiming of the two guns of the S.E.5a. The brigade gunnery officer pointed out that if their muzzles were aligned parallel, the bullets at 200 yards would form two groups that would just overlap, giving the best possible spread. Brooke-Popham replied on behalf of the GOC that they were to be left converging, as designed, to get the greatest weight of bullets into the target area.

I would guess the best range for convergence would be 150 to 200tds. Pilots being officers may have been allowed to change that range.

[Epee]

Might it have had something to do with the SE5a's flight attitude? Perhaps it pitched slightly nose-down?

[mik]

I don't know but 5 degrees pitch seems more than slightly. I found "aeroplanes of the royal aircraft factory" page 112 says the guns are set at 5 degrees and converge at 150 yards.
Elsewhere in the book pictures of SE5's with the old greenhouse fitted show the aldis sight set parallel to the cowling.

[John McKenzie]

IF the Aldis were set parallel to C/Line , (assuming no bullet drop at this close ranges) , and with the Vickers set at 5 deg & the Lewis at slightly less than 5 deg angle , up from the aircraft C/Line , .........Then ,.....:-

Over 150 yds range , the "convergent point" would be about 39 Ft Above the Aldis target sight line ,
or
At 50 Yds range ,....the convergent point will be 13 Ft above the Aldis target sight line .

Pretty obvious that your info' is wrong .

[mik]

John You are correct. lately I have said this more than once. You can't believe everything you read in a book.
However I have spent many long years researching how/why the SE5a armament was setup this way. My book references are all I could find on the subject.
the parallel aldis sight pictures with the greenhouse are all early SE5's not SE5a's. I suspect their guns might have been parallel to line of flight. The only aircraft I know for sure with a parallel vickers was Albert Ball's machine.

The aldis seem to be set at about 5 degrees If You accept that the guns converge at 150yds. The pilots must have been shooting up somewhere above them. The only possable advantage with this may have been in a tight banked turn you would normally turn tighter than your opponent to lead him. Where the SE5a would not have to turn so tight.

[mik]

Someone called Dan San Abbot from California has said in an old thread that the SE5a flew 5 degrees nose down. I find this hard to believe, however I DO BELIEVE IT. As To greenhouse equipped SE5's with guns parallel to the cowling I think they must have been rigged to fly different

[errolmartyn]

Originally Posted by mik

John You are correct. lately I have said this more than once. You can't believe everything you read in a book. . . .

or in a forum . . .

Errol

['14-'18aviationcollector]

Originally Posted by mik

Someone called Dan San Abbot from California has said in an old thread that the SE5a flew 5 degrees nose down. I find this hard to believe, however I DO BELIEVE IT. As To greenhouse equipped SE5's with guns parallel to the cowling I think they must have been rigged to fly different

The angle of incidence is also 5 degrees, so I have often wondered about that too. I have seen at least one in flight photo which indicates that the SE5a flew nose down. If so, it explains the reason for the Vickers machine gun and its' sights being set at 5 degrees positive incidence. The SE5a tailplane has an adjustable incidence mechanism. From memory the range is 0 degrees (or perhaps even -1 degrees) through to 5 degrees positive incidence. When the adjustable tailplane incidence is set to a positive incidence, it would tend to make the SE5a fly in a nose down attitude.

[mik]

Three reasons to believe.

Absence of a better theory.

I am aware he Grumman Hellcat flies 3 1/2 degrees nose down.

Dan San explained where the wings guns and tail were in relation to each other.