Armored seats references

[Romani]

In Chapter 2, "The riders of the clouds" of "The Friendless Sky" by Alexander McKee (1964) I came across the following passage:
(I have a Spanish edition so I'm translating back into English it surely will differ from the original)

(preceding lines about Oswald Boelcke)

"Boelcke requested to join the Air Service, and little before the start of the war found himself piloting one-seaters, after only four hours of training. His aircraft, in itself quite unable to climb, suffered a engine breakdown , and minutes later, Boelcke, sitting in a wheat field inspected the damage: one propeller blade broken and the landing gear disabled. Constantly following the tactic of ignoring orders, he managed to arrive to the front when the German army was still advancing across France , and on his own initiative and without any authorization he made a reconaissance flight over the Argonne, in the course of wich he was subjected to a intense shooting, and one of the bullets embedded in the armored plate his seat had The pilots of the RFC had requested armored plates when it was made obvious that airplanes could be shot down by ground fire , but as the official British historians complacently observe, the old-time commanders didn't let themselves to be carried by the innovation and it was not introduced until 1918, when the war was almost ending. Afterwards, the plate was forgotten again until 1939, year in wich Lord Beaverbook had to argue energically to attain, at the same time as the plate, bulletproof glasses for the RAF cockpits"


On reading this story many years ago, I assumed then that the plate was a backplate, and the headrest fairing on some aircraft was meant to extend the protection to the head, but when I raised this subject in the forum for the first time, that notion was put to rest.

But that's a lot of metal, and quite heavy. In a rough estimate, it takes 10mm of steel plate to stop a .30 caliber (7.xx mm) bullet at a range of below 200 meters. For comparison purposes, the armored seat and overhead protection in the Messerschmitt Bf109 F of WWII was 8 mm, so no back plate on WWI planes.

But then again, when I read again this extract, I realized that the author must be referring to the seat not the back of it. And then it makes much more sense. It's a lot less of steel to cover the hindquarters of the pilot, and if it was meant as protection against ground fire, it doesn't need to be as thick. When firing upwards bullets lose velocity and penetration much faster, thereby shortening the lethal range, so a pilot could be safe flying at 200 meters directly overhead the ground fire with half as much steel plating, let's say 5mm thickness.. judging by the size, thickness and weight of a German helmet I have around, an armored seat to cover the rearguard and the family's jewels of the pilot could be done for less than 5 kilos.

I think these figures are valid for standard copper jacketed ammunition, not steel jacketed armor piercing bullets. For contemporary comparison the first British tank, the Mark I of 1916, had an armor thickness of 10mm, as the Germans introduced armor piercing rounds in their machineguns, this was increased to 12mm in the Mark IV of 1917, and 15mm in the Mark V of 1918.

So the concept seems plausible, and there are three sources mentioned that can confirm it, Boelcke's biography, the official history of the RFC-RAF, and the request must be filed somewhere in some archive.