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Hi!

I just wondered why the Airacobra, Kingcobra and the early Typhoons had car-like side-doors?

It probably made entering the cockpit easier, but since when was creature comfort a driving force in fighter design? Furthermore, pilots didn't seem to like it and it made bailing out rather more difficult than easier. Nevertheless, it was fashionable with aircraft designers at some time and there must have been some perceived advantages. But which?

BTW, how many designs used such doors? I can only think of the Bell fighters (including the Airabonita?) and the Hawker Typhoon (including Tornado). Do you know any other?

Any ideas welcome!

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Im guessing it was one of a few possible reasons. Most likely it was easier to take off the shelf designs from automotive manufacturers and incorporate them ? Two it was easier for incorporating rearward visibilty for a pilot. The technologies for fully blown hoods and canopies were just coming into being when these planes were designed. 

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6 minutes ago, Corsairfoxfouruncle said:

Most likely it was easier to take off the shelf designs from automotive manufacturers and incorporate them

I don't think they were actual car doors.  They're just called that because they hinge sideways.

 

The other option at the time was a sliding or side-opening canopy with high sills, and a cockpit into which the pilot lowered himself.  A car door would certainly be easier than that and the designers may have thought that it would be easier to get out that way too, especially if the canopy might have got stuck.  A further option was a sliding hood with a bottom-hinged door, as with the Spitfire.  At least one design, the P-39, had two doors, which suggests redundancy being built in to allow for one being damaged.  Practical experience might then have shown that neither location for a side hinge is ideal, while a bottom hinge is easier to use in many flight conditions.  What seemed a good idea on paper wasn't so good in real life; cockpit access certainly wouldn't have been the only feature where that happened.

 

The question of framed -v- blown canopy is separate.  A car door would have been trickier to build into a blown canopy arrangement, but the car door was probably going to have been abandoned either way.

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Another factor with the P-39 is that the fuselage structure is based around a strong 'keel' and integrated roll-over structure on which the engine, prop shaft and armament is fitted. This design allowed large doors to be fitted without compromising the rigidity of the fuselage. Only the rear fuselage is stressed as a monocoque. If you look at a P-39 with the servicing panels detached you can easily see that the skin doesn't carry load. You can also easily make out the integrated (inverted 'U' shaped) roll-over structure/ firebreak immediately behind the cockpit. As well as incorporating the firewall, the pilot's seat also 'hangs' from this structure. 

 

 

Bell_P-39_Airacobra_center_fuselage_deta

Edited by Killingholme
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Good point! I think the front fuselage of the Typhoon also was not monocoque, but rather a steel-tube frame. But does this design easily allow for large doors? Probably yes. I think the Hurricane (similar construction) also had access doors which, however, were only removed for maintenance. 

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Perhaps the front hinged doors were designed to be completely released in an emergency (don't know enough about P-39/P-63 designs) but I would think opening that front hinged door against the slipstream would be virtually impossible.

Edited by Chuck1945
add a missing word
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28 minutes ago, Killingholme said:

firebreak

I doubt it was much of a firebreak ? Yeager spent a few weeks in a hospital at Tonopah Nevada due to burns suffered on his inner thighs. He was in a maneuver when the engine caught fire. The flames traveled forward on the drive/prop shaft and crept up his legs before he could bail out. He was supposed to be married the following weekend and Glennis traveled to Nevada to be married.

 

1 hour ago, pigsty said:
1 hour ago, Corsairfoxfouruncle said:

 

I don't think they were actual car doors.  They're just called that because they hinge sideways.

 Let me clarify ... The design was copied from the “idea” of car doors. 

 

21 minutes ago, Chuck1945 said:

Perhaps the front hinged doors were designed to be completely released in an emergency (don't know enough about P-39/P-63 designs) 

I do believe they were “jettisonable” for emergency egress. 

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3 hours ago, Chuck1945 said:

Perhaps the front hinged doors were designed to be completely released in an emergency (don't know enough about P-39/P-63 designs) but I would think opening that front hinged door against the slipstream would be virtually impossible.

It's not impossible. On a light aircraft like a Piper Cherokee, unlatching the door will cause it to open an inch or so, causing a dreadful racket in the process. The pressure inside the cockpit is higher than that outside. Opening the door on take-off is a favourite tactic of flight instructors with their newbie students to show that the aircraft is perfectly flyable with the door ajar. However, you generally can't close and latch the door while in the air so you have to come back and land to get it latched up again.

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13 hours ago, Chuck1945 said:

Perhaps the front hinged doors were designed to be completely released in an emergency (don't know enough about P-39/P-63 designs) but I would think opening that front hinged door against the slipstream would be virtually impossible.

Just because of that I have wondered why the hinges were not on back edge of the opening.

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Presumably because of the possibility of inadvertent opening/failure of closure mechanism which could lead to the door being ripped off its hinges and hence severe damage to the aircraft, notably the tailplane?  Having the door hinged at the front is a fail-safe approach.

 

It's worth pointing out that fighters aren't the only aircraft - getting into the cockpit through a car-type door was seen elsewhere in the late 1930s.  For twins of course the presence of the propellers would be a deterrent yo this design approach.

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Apparently the left door on the P-39 can be jettisoned, I have seen photos of P-39s in the Pacific landing with no left door. The text with the photo stated "It was standard practice to jettison the door before an emergency landing in case of fire."

 

Garry c

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I have been led to believe that in the earlier WWII years the ability to produce such a large and blemish free Perspex was a factor hence the car doors rather than the bubble. I may well be misinformed here however.

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Fighter canopy design prior to the fully blown perspex is an interesting topic. The primary trade-off between low drag and good visibility was explored in a lot of ways, and of course considerations like emergency jettison, rollover protection, and aerodynamic effects on the empannage were also important.  I think the variety of different designs used indicate the perfect balance was hard to achieve.

 

Every engineering decision is a compromise, and thousands are made with every design.  In hindsight the "car door" canopy may not have been the best solution, but neither was it radically worse than the contemporary choices.

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Two reasons: the first, so you can wind the window down when it gets warm, and secondly; easier to get your parking ticket from the machine.

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3 hours ago, Darby said:

Two reasons: the first, so you can wind the window down when it gets warm, and secondly; easier to get your parking ticket from the machine.

You mean the pilot could wind down the window and say "one Quarter Pounder with cheese, large fries, extra onion rings and a super-size coke, please"?

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