
Abraham Wald's Work on Airplane Survivability (1984) [pdf] - tjalfi
https://people.ucsc.edu/~msmangel/Wald.pdf
======
supernova87a
It's a work that people love to make Youtube videos out of, and is
interesting. "Where are the missing bullet/flak holes?" is the question people
should be asking, rather than just armoring the places that are obviously
bullet-ridden. The paper is much more technical than you would think from the
popular tale (Lagrange multipliers, etc).

I believe they did other story-worthy statistical feats, like estimating the
size of the German tank fleet by observing the serial numbers of captured
tanks.

~~~
jonah
Aahh, yes, the German Tank Problem[1]. Also more complex than it would
initially seem.

[1]
[https://en.wikipedia.org/wiki/German_tank_problem](https://en.wikipedia.org/wiki/German_tank_problem)

------
seesawtron
I read about this in Daniel Kahneman's "Thinking Slow and Fast" where this was
listed under possible "suvivorship biases" i.e. we draw conclusions from data
that survives but forget about the unseen data. For example, we read stories
about how someone with a simple startup idea became a millionaire but never
hear about those who tried and failed hence creating a biased view on
startups.

------
tjalfi
(submitter)

Wald's WWII memos were reprinted in the 1980s and are available here[0].

[0]
[https://web.archive.org/web/20140814122810/https://www.cna.o...](https://web.archive.org/web/20140814122810/https://www.cna.org/sites/default/files/research/0204320000.pdf)

------
redis_mlc
I study WW2, and the US had such fundamental problems with bomber design that
you could say they were of doctrine in nature.

The B-17 "Flying Fortress" had lots of guns and a crew of 10, but couldn't
defend itself against German fighters. It's payload ended up being the same as
the 2-man British Mosquito bomber.

The B-29 was the first pressurized bomber, yet that just made it expensive to
build since bombing accuracy at 20k feet is random, and Curtis Lemay ended up
using it at 5k feet, with napalm.

~~~
jabl
> The B-17 "Flying Fortress" had lots of guns and a crew of 10, but couldn't
> defend itself against German fighters. It's payload ended up being the same
> as the 2-man British Mosquito bomber.

To make a more apples to apples comparison, one should replace the B-17 with
the British heavy bombers, who often flew on the same missions as the
Mosquito. The British heavies were similar to the American ones (though
somewhat higher bomb load and less defensive guns). The interesting thing is
that the loss rate for the Mosquito was an order of magnitude less than for
the heavies (which was beyond appalling). It was just so fast that it was very
difficult to catch for the Luftwaffe night fighters, and of course by being
faster it spent less time in flak barrages as well.

Of course one could argue that the slow heavies presented much juicier and
easier targets for the Luftwaffe and the flak, so they didn't bother going
after the Mosquitos. And thus if Bomber Command had switched from heavies to
fast unarmed ones like Mosquito the loss rate would have climbed. Still hard
to see how it could have reached the levels it factually did for the heavies.

An interesting tidbit here is from Freeman Dyson, who served as an analyst in
Bomber Command during the war. He had calculated that the loss rate would be
reduced by removing all, or most, defensive armaments. This was based on
reduced drag and weight increasing the speed, and also that interviews with
aircrew who had been shot down and (miraculously) survived and made it back to
England revealed that most never knew what hit them. But this proposal was
shot down, as the myth of the heroic gunners protecting their mates was so
strong.

~~~
cpgxiii
_interviews with aircrew who had been shot down and (miraculously) survived
and made it back to England revealed that most never knew what hit them_

The particularly depressing part of this story is that for months RAF crews
were reporting attacks they couldn't see coming, and the RAF ignored these
reports and chalked these losses up to flak. What _was_ happening was the
Luftwaffe had observed that RAF heavy bombers lacked belly gun turrets and had
essentially zero downwards visibility, and had developed the upwards-facing
_Schräge Musik_ gun mounts to attack from below. What was also happening was
that RAF bombers were being equipped with _Monica_ tail warning RADAR in an
attempt to detect pursuing night fighters more easily, but the Luftwaffe had
quickly developed detectors that allowed night fighters to directly home in on
these bombers instead, while still avoiding being detected by _Monica_ sets.
Together, these were responsible for much of the severe losses suffered by
Bomber Command in the winter of 1943-1944.

~~~
jabl
> Luftwaffe had observed that RAF heavy bombers lacked belly gun turrets and
> had essentially zero downwards visibility, and had developed the upwards-
> facing Schräge Musik

My understanding was that the point behind attacking from below wasn't so much
the bombers lacking a belly turret as the bomber being silhouetted against the
night sky, whereas detecting a plane by looking downwards towards the dark
earth was almost impossible.

And yeah, the history of early electronic warfare is fascinating. All the
things they came up with, and the counter-measures developed amazingly quickly
etc.

~~~
cpgxiii
There were plenty of other reasons to attack from below - interest in the
tactic predates the war - but I don't think the tactic would have been
anywhere near as effective if RAF heavy bombers had been equipped with belly
turrets (and armed with something better than the basically useless .303
machine guns). Entirely different tactics were used against the USAAF
formations in daylight, where a slow overtaking approach from below would be
far to vulnerable.

 _whereas detecting a plane by looking downwards towards the dark earth was
almost impossible_

This would be true on the long approach to the target, but once near the
target area, bombers would be silhouetted from below by searchlights, flares,
and the burning city beneath them. Enough light was available from these
sources for the Luftwaffe to use _Wilde Sau_ single-seat "day" fighters at
night.

