WWII Aircraft RAM-D (Reliability, Availability, Maintainability, Durability)

[ThomasP]

I have run across a fair amount of information on this forum that goes to the subject of RAM-D but I would like to have it more concentrated if possible. I would particularly appreciate official information (ie from the various Air Forces, procurement organizations, manufacturers, tests, etc.) but anything that seems to be from experience is also welcome.

I will start out with the following which I found somewhat humorous as well as informative.

A quote from James 'Ginger' Lacey of 501 Sqdn, the second highest ace from the BoB period.

"I'd rather fly in a Spitfire but fight in a Hurricane - because the Hurricane was made of non-essential parts. I had them all shot off at one time or another, and it still flew just as well without them."

Between the BoF and BoB Lacey was shot down in or forced to land a damaged Hurricane 9 times.

He later flew Spitfire Vs and VIIIs.

 

[Zipper730]

I have run across a fair amount of information on this forum that goes to the subject of RAM-D but I would like to have it more concentrated if possible.

What information do you have so far? There's probably a fair amount you have to start with. That said, I'll call in some of our forum experts

BiffF15 S Shortround6 swampyankee syscom3 W wuzak X XBe02Drvr

 

[Crimea_River]

I read that there was a joke among German pilots in which Willi Messerschmitt would visit crash sites of his airplanes. He would look for parts that didn't break and make them lighter on his next designs.

 

[ThomasP]

I realize the way I phrased the post header is somewhat general and maybe it is trying to cover too much.

I found michael rauls post The importance of availabilty. interesting, and have always found the numbers for this kind of thing interesting, both from the military history/operational viewpoint and from its engineering aspect.

Example:

From what I have read the B-17 was apparently more rugged (Durability) than the B-24, at least as evidenced by its lower loss rate due to Flak damage. I say this is probably correct because while I have read from different sources that this was true, I have never run across anything (so far) that said the opposite was true. But was it better in term of taxiing under comparable ground operating conditions and at similar loads?

Was it easier/harder to fix the damaged B-17 (Repairability) than the B-24?

Did it require more/less man-hours to service (Maintainability) than the B-24?

What was the expected/actual service life (if it was not destroyed prematurely) between rework/rebuild/overhaul? (this would apply under Maintainability, and Durability). In other words, how many flight hours, sorties, operations would the airframe last before it became not worth it to rebuild?

If we add in the P (Producibility) in PRAM-D, when the B-24 came into service (ie the brand new factory built) and the time period (ie designed several years later than the B-17) probably meant that the B-24 was easier to manufacture than the B-17. But was it really? Also what was the actual cost difference?

Answers to the above would could give a good feel for why a B-17 or B-24 squadron had higher operational rates than the other (Availability).


Another example is the Hurricane vs the Spitfire.

The Hurricane, by all accounts that I have run across (so far), wins in Producibility and Repairability (particularly in the field). The Hurricane was also superior in turn-around time (ie refueling, rearming, re O2, etc).

The Hurricane (again by pretty much all accounts) was more rugged (Durability) than the Spitfire in day-day operations, whether on land or aboard carriers .

But did the Hurricane take more/less routine maintenance than the Spitfire (due to its wood and cloth covered structure aft fuselage, for example)?

The above causes me to conclude that the Hurricane had a higher inherent Availability, but other than during the BoB I do not have any hard numbers to prove this.


As I said, I find this stuff interesting, and it seems like others do too. I am trying to get a feel for the related problems the different nations encountered. Plus I figure this is a good subject for people to put up information relative to favorite aircraft (and have endless discussion/argument).

I realize the subject is possibly too large for a single post (maybe it would be better to separate it into different aircraft types, nationalities, etc?

 

[K5083]

What is the good of availability if your aircraft is inferior? Hurricanes may have had better durability, all the anecdotal evidence points that way, but when it came to establishing air superiority, which is what the aim of a fighter is, they were usually on the wrong end.

As for B-17 vs B-24, it is all detail except for the loss rates. On a level playing field, B-17 lost fewer aircraft . B-24 may have been superior in many ways, ground handling, range, whatever, but it was subject to higher losses. Whether those losses were related to effects of damage, and how much, would be interesting to know

 

[ThomasP]

Hey K5083,

re: "What is the good of availability if your aircraft is inferior?"

Some of your question is addressed in michael rauls post The importance of availabilty.
and Friendly Fire's post Gloster Meteor vs Messerschmitt Me 262, one-vs-one dogfight.

Another answer that has significant effect is that, as long as the inferior aircraft is in the area, the superior aircraft is at risk. This is born out by the fact that in WWII (and before? after?) somewhere around 8 out of 10 (I have also read 9 out of 10) shoot downs occur without the pilot being aware that he is about to become a positive statistic in the other guys record. My understanding is that this ratio is as much about the inability of the pilot to keep track of the enemy aircraft after the battle starts (ie situational awareness) as it is that the enemy was never seen at all (ie total surprise). I have not read any numbers on the ratio of shoot downs due to loss of situational awareness vs those due to total surprise.

Just pre-war, the prototype F4F (monoplane) and the F2A were test flown against the F3F in mock dogfights. There is no question that the F4F and F2A were faster (both could do over 300 mph vs the F3F at ~255 mph) and hence could force or avoid a fight if whey wanted to when aware of the enemy (at least for the most part), but it was found that the only way for the monoplanes to reliably survive the fight was to leave the area after the initial attack. (These tests are referenced in the ?* on the F4F).

Even near the end of the war this phenomena seems to have held true. The PTO particularly seems to demonstrate this. The USN carrier groups would have had a difficult time doing their job if they could only have launched half squadrons due to availability issues, despite the qualities of the F4U and F6F.


*Edit: Apparently memory fails me. I just checked the F4F Profile Publication and it does not tell the story of the tests I referenced. I will try to find the actual source.

 

[ThomasP]

P.S. I agree, it would interesting to know.