Thanks for that seems it was pretty advance technology if it pre dated Tiffy and Hurricane ground attack aircraft.

I dont suppose anyone has a picture of a Lysander with cannons?

Graham, you’ve sent me a pm but I cannot reply until you clear out your inbox. Laterz.

done

Was it the RAF’s first cannon armed plane?

Cannot think of another, after all what other RAF aircraft was cable of mounting cannon at that time?

Thanks!

Why would it? Newton’s third law applies; “To every action there is an equal and opposite reaction.” Equal being the critical part. The Lysander was a reasonably large single-engine aircraft, with significant mass, similar to that of most cannon-armed single seat fighters of the time. For some reason, as soon as cannon are mentioned in non-fighter types, people seem to assume that on firing it would drop it out of the sky, despite the fact that a projectile would have to be fired a lot faster or be a lot heavier than most guns were capable of at the time. Vibration from firing was a different issue, and did cause problems on types like the Tetse Mozzie and the cannon armed B-25 at servicing, but the myths of ‘stopping in mid air’ are just hyperbole.

Just to be clear – it was a bit more than a ‘lash up’ and was devised before the risk of an invasion occurred.

They probably had a SPAD or two in service in April 1918.

Certainly there were the COW armed fighters and flying boat in the 1930s.

By 1940 cannon were a reasonably widely used option in fighters and a few bombers if you consider the scene worldwide. Machine-gun only armament was still widespread, but certainly in the process of being supplanted.

Regards,

I would have to do some serious maths to work out the exact forces involved but the weight of the shot combined with the velocity it leaves the barrel would create quite a force pushing backwards on the legs.
When you consider the positioning of the guns on the legs it would have an increased effect on stability a bit like a spanner turning a nut.
I know from using flight sims that firing cannons do slow Spitfires down which is a heavier and more powerful aircraft than a Lysander so there is a considerable force invoked.
It seems to me that some effect would be felt on the stick of a Lysander how much that effect would be would like i say take some working out, however at the very least it would affect sighting of the guns.
It certainly caused some problems as they were not adopted operationally.

…can’t resist a go at that! :diablo:

Two Hispano-Suiza 20mm cannon firing 60 rounds each of AP-T, weighing 168g, at a muzzle velocity of 880m/s (in about 5 seconds)…

…one Westland Lysander with an empty weight of say 2000kg (assumed to be standing still in mid-air for ease of calculation).

If the Lysander fired all 120 rounds the total momentum of the cannon ammunition would be:

120 x 0.168 x 880 = 17,741 kgm/s

If all that momentum is absorbed by the Lysander airframe (excluding blah, blah, blah):

17,741 kgm/s = 2000 kg x V m/s

V = 8.87 m/s

V = 19.85 miles-per-hour

So a stationary (empty) Lysander will be moving backwards at about 20mph by the time the cannon ammunition is exhausted…

…so a moving Lysander will lose about 20mph when the cannons fire (all their ammunition).

A Lysander at maximum take-off weight (2877kg) will only lose about 14mph from its speed.

(Awaiting somebody to spot a ‘school-boy-error’! :o)

This is good stuff first my comments on flight Sims earlier was meant to Illustrate the point that firing cannons do slow aircraft down I would not suggest a flight sim is any where near accurate it just in my experience when trying to catch an EA where both aircraft are going flat out it firing the guns was not a good idea unless you were guaranteed a kill shot as you lost AS and fell further behind.
Whether they are perfectly accurate in the amount of speed lost is irrelevant, the fact it was factored in as best they could, therefore you would have to accept that it happens.
The calculations made above back this up and are more significant than I would have expected. The fact that these guns are very low down on the UC they would have a levering effect on the fuselage, enough I would think as I previously said to at least badly effect sighting of the Guns.