P-40s on Clark Field

[fredleander]

The gun chargers where not directly connected to the landing gear in any way. They had there own feed from the hydraulic system and the lines went directly from the chargers to the guns. You could have a leak and lose fluid in the system but that would not cause the gear to collapse. The gear on a P-40 will stay down with no fluid in the system.

The technical order to remove them came out in October 28, 1942.

Brandon

I suppose you mean 1941...

Fred

 

[Deuelly]

As I understand it, the reason behind the commotion was that it was suspected that the gun charging mechanism, also part of the plane's hydraulic system, in some way could have, at one stage, created a problem for the under-carriage part of the hydraulic system. Exactly how this came about I do not know but it was allegedly the reason why it was decided, for a period, anyway, to disconnect the charging mechanism from the hydraulic system. As we know, when this maintenance procedure was cancelled the technical guys in the Philippines were not informed, or the information was mislaid.

Looking at the instructions on the charger panel there is obviously a sort of connection between the two systems. Wonder if this panel was the actual one in 1941 - or a later version.

Fred

As I stated in my original post, the chargers are connected to the system and can cause it to lose fluid. This will not cause the gear to collapse. Pilots should also still be able to put the gear down. The document does state faulty operation and continual maintenance as the reason for removal.

The panel is from an "D", "E" or early "K" model. They all used the same panel. The document I attached is dated 1942. Also note that in it it states Curtiss released its service bulletin in August, 1942 not 1941.

Not saying anything either way. I'm just presenting the information I have and what I know of the system. I would love to see the documentation from 1941 that you have though. I don't have it in my collection of Service letters or Engineering Change Orders. Or was it one of those things the mechanics did without official order? If that's the case then the information would probably not have left Clark Field without someone violating protocol.

I'm always interested in learning more about these aircraft. You stated "as we know", but I have never heard this so want to learn.

Brandon

 

[fredleander]

As I stated in my original post, the chargers are connected to the system and can cause it to lose fluid. This will not cause the gear to collapse. Pilots should also still be able to put the gear down. The document does state faulty operation and continual maintenance as the reason for removal.

I am not sure if we are talking about the same incident(s)....

The panel is from an "D", "E" or early "K" model. They all used the same panel. The document I attached is dated 1942. Also note that in it it states Curtiss released its service bulletin in August, 1942 not 1941.

….as what is referred to earlier in this thread was the particular problems with the P-40Es in the Philippines in December 1941...(which is why I wondered if your "1942" was a misprint)..a technical bulletin - or instruction - at that time required the hydraulic charger system to be disconnected - for what reason I do not know and I have not read the actual bulletin. The gist of it was that this bulletin was revoked before December 1941 but this information allegedly did not reach the Philippines before the war broke out. This came on top of the other problems they had with their .50 calibre machine guns.

Not saying anything either way. I'm just presenting the information I have and what I know of the system. I would love to see the documentation from 1941 that you have though. I don't have it in my collection of Service letters or Engineering Change Orders. Or was it one of those things the mechanics did without official order? If that's the case then the information would probably not have left Clark Field without someone violating protocol.

My reference is Bartsch's book "Doomed at the Start", where he describes the problem. According to him the alterations on the hydraulic system were not initiated by the mechanics on the Philippines.

I'm always interested in learning more about these aircraft. You stated "as we know", but I have never heard this so want to learn.

Brandon

As am I.... I wrote "as we know" because others here have stated that they have read the same book(s). I was sure you had, too. Sorry.

Fred

 

[Deuelly]

I am not sure if we are talking about the same incident(s)....



….as what is referred to earlier in this thread was the particular problems with the P-40Es in the Philippines in December 1941...(which is why I wondered if your "1942" was a misprint)..a technical bulletin - or instruction - at that time required the hydraulic charger system to be disconnected - for what reason I do not know and I have not read the actual bulletin. The gist of it was that this bulletin was revoked before December 1941 but this information allegedly did not reach the Philippines before the war broke out. This came on top of the other problems they had with their .50 calibre machine guns.



My reference is Bartsch's book "Doomed at the Start", where he describes the problem. According to him the alterations on the hydraulic system were not initiated by the mechanics on the Philippines.



As am I.... I wrote "as we know" because others here have stated that they have read the same book(s). I was sure you had, too. Sorry.

Fred

I understand Fred. I work quite a bit with P-40s so I'm always curious about modifications and their origins. My information was the only documented removal order of the gun chargers I knew of. In the warbird world there is a lot of contradicting information. A lot of things that went on in the field were never talked about. Curtiss was pretty good about making changes to the P-40 that were causing problems in the field. I'm amazed it took them a year to put out a service bulletin for the problem. Maybe Clark field never reported it to curtiss either? I'll have to read through Bartsch's book to understand the circumstances better.

Brandon

 

[MiTasol]

Does anyone know about the automatic gun charging systems on the early P-40s? (1941) How the guns were manually charged?

Among the many problems P-40 ground crews at Clark Field had in readying the pursuit squadrons for war in the fall of 1941 was the hydraulics for the automatic gun charging system was linked to the landing gear. In the summer of 1941 word came from Wright Patterson to disconnect the gun chargers or the wheels could collapse. They solved the problem at W-P by October but no one informed Clark before war started.

Thanks if you can shed some light?

The gun chargers where not directly connected to the landing gear in any way. They had there own feed from the hydraulic system and the lines went directly from the chargers to the guns. You could have a leak and lose fluid in the system but that would not cause the gear to collapse. The gear on a P-40 will stay down with no fluid in the system.

The technical order to remove them came out in October 28, 1942.

Brandon

I am reasonably confident there were actually at least two TOs on removing the chargers.

The first one pre Pearl Harbor, as referred to in Doomed at the Start, which stopped the use of the chargers because leaking hose problems caused the aircraft to lose enough fluid that the landing gear could not get enough fluid to fully extend and lock the gear. This will cause the gear to collapse when the aircraft lands because both systems, and the flaps, used the same hydraulic reservoir and pumps. Once better flexible hoses were developed the first one was rescinded and better hoses fitted but whether this was pre or post Pearl Harbor I am yet to discover.

The October 28, 1942 one that permanently removing them from the system came later for the reasons shown in the TO provided above but it may again have been rescinded as the Feb 43 armament manual still covers the hydraulic charging as well as manual charging. Certainly every E model I worked on in the 60s and 70s had the full gun charge panel still fitted and plumbing in the wings.

There were a number of other P-40 armament TOs at the time that I know existed but I have been unable to find.

One for instance, in early 42, totally changed the gun ports and blast tubes as shown below is confirmed in a recent letter from the NASM and I am purchasing a copy.

 

[MiTasol]

How the guns were manually charged?

See the attachment for both hydraulic and manual charging. You will note the chargers would tend to get in the way while fitting the guns so the short flex hoses would probably have got a large amount of twisting and bending - not great for reliability on those early types of hoses. Fine on modern hoses.

This note may suggest another reason they were deactivated - if the pilot fumbled the procedure he would lock the guns in the rear position.

 

[Deuelly]

I am reasonably confident there were actually at least two TOs on removing the chargers.

The first one pre Pearl Harbor, as referred to in Doomed at the Start, which stopped the use of the chargers because leaking hose problems caused the aircraft to lose enough fluid that the landing gear could not get enough fluid to fully extend and lock the gear. This will cause the gear to collapse when the aircraft lands because both systems, and the flaps, used the same hydraulic reservoir and pumps. Once better flexible hoses were developed the first one was rescinded and better hoses fitted but whether this was pre or post Pearl Harbor I am yet to discover.

The October 28, 1942 one that permanently removing them from the system came later for the reasons shown in the TO provided above but it may again have been rescinded as the Feb 43 armament manual still covers the hydraulic charging as well as manual charging. Certainly every E model I worked on in the 60s and 70s had the full gun charge panel still fitted and plumbing in the wings.

That's interesting, on the P-40's you can only discharge the hydraulic fluid down to the standpipe in the tank with the electric pump and actuating the gun chargers. After that you go to the hand pump, and at least on the P-40's I've dealt with, you are still able to get the gear down. On most the early models, like the P-40E, you even had the emergency hand pump to use after that. Maybe it was more of a pilot training and mechanical issue?

There were a number of other P-40 armament TOs at the time that I know existed but I have been unable to find.

One for instance, in early 42, totally changed the gun ports and blast tubes as shown below is confirmed in a recent letter from the NASM and I am purchasing a copy.

View attachment 557261
View attachment 557262

I've seen the style below on some P-40 wreckage. It looks identical in installation to the picture above. Curtiss started changing production over to the later style in late 1941. The official T.O. came out some time in early 1942 I believe.

Brandon

 

[MiTasol]

That's interesting, on the P-40's you can only discharge the hydraulic fluid down to the standpipe in the tank with the electric pump and actuating the gun chargers. After that you go to the hand pump, and at least on the P-40's I've dealt with, you are still able to get the gear down. On most the early models, like the P-40E, you even had the emergency hand pump to use after that. Maybe it was more of a pilot training and mechanical issue? Brandon

I think it was partly pilot training and a lot that many of the crews were operating under stress and forgot what the significant "minor" details of the procedures were so stuffed them up. In particular I think they may well have not realized/remembered how many full pump strokes are required to extend the gear against the airflow (it is nothing like in a hangar on jacks were gravity does most of the work). Stroking the pump only half travel produces well under half the fluid transfer.

Also remember there were no emergency checklists carried on these aircraft - unlike all modern aircraft.

 

[Deuelly]

I think it was partly pilot training and a lot that many of the crews were operating under stress and forgot what the significant "minor" details of the procedures were so stuffed them up. In particular I think they may well have not realized/remembered how many full pump strokes are required to extend the gear against the airflow (it is nothing like in a hangar on jacks were gravity does most of the work). Stroking the pump only half travel produces well under half the fluid transfer.

Also remember there were no emergency checklists carried on these aircraft - unlike all modern aircraft.

I agree, the work it takes in flight usually makes you want to stop about half way through and take a break. You also usually beat your hand up pretty bad on the radio tuner box when your nervous and pumping like crazy.

I think the only emergency procedure listed in the whole plane is the one on that placard by the hand pumps. Who wants to have there eyes looking at the floor trying to read a beat up placard when things are going wrong.

Brandon

 

[waroff]

- P40, P40G, B, C: "wing guns are mechanically charged by a cable and pulley system with modified A-2 handles located below the instrument panel at the center of the cockpit"
- P40 D to L: " the guns are charged hydraulically by means of three valves located below the main switch box in front of the pilot. To charge guns, turn handle clockwise 140°, then push. To safety or lock the guns, match the point of the handle with red mark and then push."
- P40, some F, L, K and M & N: " charge each gun with the ground charger stowed on the gun bay access door"

 

[MiTasol]

I agree, the work it takes in flight usually makes you want to stop about half way through and take a break. You also usually beat your hand up pretty bad on the radio tuner box when your nervous and pumping like crazy.

I think the only emergency procedure listed in the whole plane is the one on that placard by the hand pumps. Who wants to have there eyes looking at the floor trying to read a beat up placard when things are going wrong.

Brandon

Oh yea.

I have never had to do it in flight on the P-40 but I have cranked the Avro Anson gear down in flight. The manual says 180 turns but it felt like five times that before the green lights came on and the ergonomics were what is politely called shit.