4 ms·

WW2: If planes are back with no damages on the tails, add armor on the tails... [pdf]

22 points by napolux 12y ago

gk1 12y ago
Where do you see such a conclusion in this document? From Page 88 (emphasis added): > "This analysis of the hypothetical data would lead to the conclusion that the plane is most vulnerable to a hit on the engine area if the type of bullet is not specified, and is most vulnerable to a hit by a 20-mm cannon shell if the part hit is not specified. The greatest probability of being destroyed is .534, and occurs when a plane is hit by a 20-mm cannon shell on the engine area. The next most vulnerable event is a hit by a 7.9-mm machine gun bullet on the cockpit..."
- Crito 12y ago
  The point is not that tails are where you should armor planes. The title is just giving a simplified throwaway example of the idea that the analysis is based on. Key word in the title being "If".
- stan_rogers 12y ago
  The received wisdom here is that if an aircraft is capable of returning from a mission with heavy damage in a particular area, that area probably has enough strength/redundant structure already, and adding armour isn't going to accomplish much beyond adding weight. If, however, aircraft rarely or never return from a mission with significant damage to a particular area, it's probably a good indication that damage to that area is not survivable (which is why the aircraft are not returning). One needs to pay attention to the data that aren't present, or at least wonder why they aren't present.
  - gk1 12y ago
    I understand... the survivor bias... Just couldn't understand what the OP was trying to say with the title.
bluedino 12y ago
Previous discussion: https://news.ycombinator.com/item?id=1748979 https://news.ycombinator.com/item?id=1748979 But I swear I saw it a week or two ago as well.
- Zancarius 12y ago
  You did: https://news.ycombinator.com/item?id=7851927 https://news.ycombinator.com/item?id=7851927
mcfunley 12y ago
Two weeks ago I tried to explain this idea to an ex-Air Force tour guide as we were standing next to the waist guns in a B17. He said I was full of shit and that the planes flew with basically no reinforcing armor. It was kind of embarrassing.
- ceejayoz 12y ago
  Some aircraft certainly did. The Japanese Zero was notable in part for its lack of armor around the pilot and non-self-sealing fuel tanks.
- nether 12y ago
  > It was kind of embarrassing. I would be cringing at this scene, mostly at you.
  - mcfunley 12y ago
    Me too.
adolgert 12y ago
This is an interesting application, and dogged mathematical derivation, of survival analysis. We would do the same calculations today with standard Kaplan-Meier curves. Do you see the survival functions, S=1-F, in the first few pages? They also state a hazard rate, all without reference to stochastic variables. It's like seeing the mathematical version of a 1943 automobile.

22 points by napolux 12y ago

gk1 12y ago

Where do you see such a conclusion in this document? From Page 88 (emphasis added): > "This analysis of the hypothetical data would lead to the conclusion that the plane is most vulnerable to a hit on the engine area if the type of bullet is not specified, and is most vulnerable to a hit by a 20-mm cannon shell if the part hit is not specified. The greatest probability of being destroyed is .534, and occurs when a plane is hit by a 20-mm cannon shell on the engine area. The next most vulnerable event is a hit by a 7.9-mm machine gun bullet on the cockpit..."

Crito 12y ago
The point is not that tails are where you should armor planes. The title is just giving a simplified throwaway example of the idea that the analysis is based on. Key word in the title being "If".
stan_rogers 12y ago
The received wisdom here is that if an aircraft is capable of returning from a mission with heavy damage in a particular area, that area probably has enough strength/redundant structure already, and adding armour isn't going to accomplish much beyond adding weight. If, however, aircraft rarely or never return from a mission with significant damage to a particular area, it's probably a good indication that damage to that area is not survivable (which is why the aircraft are not returning). One needs to pay attention to the data that aren't present, or at least wonder why they aren't present.
- gk1 12y ago
  I understand... the survivor bias... Just couldn't understand what the OP was trying to say with the title.

bluedino 12y ago

Previous discussion: https://news.ycombinator.com/item?id=1748979 https://news.ycombinator.com/item?id=1748979 But I swear I saw it a week or two ago as well.

Zancarius 12y ago
You did: https://news.ycombinator.com/item?id=7851927 https://news.ycombinator.com/item?id=7851927

mcfunley 12y ago

Two weeks ago I tried to explain this idea to an ex-Air Force tour guide as we were standing next to the waist guns in a B17. He said I was full of shit and that the planes flew with basically no reinforcing armor. It was kind of embarrassing.

ceejayoz 12y ago
Some aircraft certainly did. The Japanese Zero was notable in part for its lack of armor around the pilot and non-self-sealing fuel tanks.
nether 12y ago
> It was kind of embarrassing. I would be cringing at this scene, mostly at you.
- mcfunley 12y ago
  Me too.

adolgert 12y ago

This is an interesting application, and dogged mathematical derivation, of survival analysis. We would do the same calculations today with standard Kaplan-Meier curves. Do you see the survival functions, S=1-F, in the first few pages? They also state a hazard rate, all without reference to stochastic variables. It's like seeing the mathematical version of a 1943 automobile.