BeechTalk - BT - Citation trivia

Username Protected · **Posted:** 30 Dec 2018, 11:10

Username Protected wrote:

As I recall, the original concept, the FanJet 500 IIRC, was to have a downward opening airstair type door. Maybe it needed to be that shape for ground clearance or something?

Very close!

It does have to do with the door that was originally fitted to the Fanjet 500 prototype. That particular door was flown only on the first prototype and not carried forward.

Attachment:

17-2.jpg

Which means the reason for the taper only applied to the first prototype and thus thousands of Citations have this feature for no reason.

More details later when I have some time...

Mike C.

Username Protected · **Posted:** 30 Dec 2018, 17:45

Very interesting! Sort of like the bulbous addition to the trailing edge of a King Air aileron.

I have a friend who upgraded from a 2+ to a CJ4, and part of the reason was one large employee that couldn’t comfortably squeeze through the tapered door.

Username Protected · **Posted:** 30 Dec 2018, 18:26

Username Protected wrote:

Very interesting! Sort of like the bulbous addition to the trailing edge of a King Air aileron.

I have a friend who upgraded from a 2+ to a CJ4, and part of the reason was one large employee that couldn’t comfortably squeeze through the tapered door.

Wow. Hell of a justification. Note to self. Hire an obese employee.

Username Protected · **Posted:** 30 Dec 2018, 20:34

Username Protected wrote:

Very interesting! Sort of like the bulbous addition to the trailing edge of a King Air aileron.

I have a friend who upgraded from a 2+ to a CJ4, and part of the reason was one large employee that couldn’t comfortably squeeze through the tapered door.

Wow. Hell of a justification. Note to self. Hire an obese employee.

Username Protected · **Posted:** 30 Dec 2018, 21:16

Username Protected wrote:

Very interesting! Sort of like the bulbous addition to the trailing edge of a King Air aileron.

I have a friend who upgraded from a 2+ to a CJ4, and part of the reason was one large employee that couldn’t comfortably squeeze through the tapered door.

Gotta take care of the employees!!!

Username Protected · **Posted:** 31 Dec 2018, 00:12

Username Protected wrote:

I have a friend who upgraded from a 2+ to a CJ4, and part of the reason was one large employee that couldn’t comfortably squeeze through the tapered door.

Or had he wanted a smaller runabout he could have bought a Mustang - the big fellow would fit through it's door!

Username Protected · **Posted:** 02 Jan 2019, 20:37

Michael,

Quote:

IIRC the door had an inflatable seal. However, having typed in and flown s/n 500-0001 for a couple of years back in the mid-70’s, I can testify that very little of that particular airplane had a correct fit with stock parts. Apparently, the airplane was mostly hand built and fitted.

Was that for Levitz?

Username Protected · **Posted:** 02 Jan 2019, 22:05

Username Protected wrote:

Michael,

Quote:

IIRC the door had an inflatable seal. However, having typed in and flown s/n 500-0001 for a couple of years back in the mid-70’s, I can testify that very little of that particular airplane had a correct fit with stock parts. Apparently, the airplane was mostly hand built and fitted.

Was that for Levitz?

It was in regard to your post above of Dec. 28, 2018.

Regards,

MM

Username Protected · **Posted:** 02 Jan 2019, 22:30

I thought we were getting the answer at midnight on the 31st?

Username Protected · **Posted:** 02 Jan 2019, 22:44

Username Protected wrote:

I thought we were getting the answer at midnight on the 31st?

Someone dropped the ball.

Username Protected · **Posted:** 02 Jan 2019, 22:55

Username Protected wrote:

Very interesting! Sort of like the bulbous addition to the trailing edge of a King Air aileron.

I have a friend who upgraded from a 2+ to a CJ4, and part of the reason was one large employee that couldn’t comfortably squeeze through the tapered door.

I know a guy who recently went from a 2+ to a CJ4. How many can there be?

Username Protected · **Posted:** 03 Jan 2019, 01:06

Answer:

The original FanJet 500 prototype had an odd air stair like ramp for the main cabin door. Not clear what Cessna was thinking.

The door had a unique closing action. It would fold up like an air stair on a hinge, but then when nearly closed, it would rise vertically to engage static pins. This effectively made it a "plug door", a door which holds without the action of latches or sliding pins. By rising vertically, the pins engaged slots that held the door.

The issue was that to open the door, it first had to drop vertically a bit, then it could fold out. The problem was getting good clearance from the door seal. By tapering the door, the gap between door and frame grew larger as the door drop vertically, this providing the clearance to open the door without rubbing the seal.

My source thinks the FanJet 500 prototype was the the only plane fitted with this kind of door. The mechanism was soon eliminated from the design in favor of a forward hinge fold out door with sliding pins, the standard door now found on all the small cabin Citations except Mustang and CJ4. But despite the change, the tapered shape was retained even though it served no useful purpose on such a door.

Thus thousands of Citations have a uselessly tapered entry door that is just a lingering vestige of a failed experiment on the very first Citation prototype.

Mike C.