Presumably UTC midnight...

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.

MM

Back in the day when we built pressure vessels for the pulp and paper industry where the door was removed and re-installed several times a day a triangular door was the easiest to install because it was self aligning. You would simply lower on corner into the hole near the apex and then slide the unit in that direction and the door would always find its best fit. Clearly the triangular door was less than optimum for the size (area) of opening so we would use oval shapes. I think a taper fit in the door design is just an extension of this principle.

Doug

I thought I knew Citations pretty well (especially the early ones) but I don't have a clue on this question. Awaiting the answer.

Small aside- went to take my type ride in a cargo 500 with the Bendix bullseye F/D. Once airborne and @10,000' the main door seal blew out. I reached over and just turned the pressurization off and asked the examiner, "you want to continue"? He did, we did, and I picked up the type rating.

I call the flight director the Apollo lunar module . I love that thing it’s cool

Yes but how many know today what the 3 rings in the center were for? :-)

to reduce FOD hazard to the original single engine vtail design

The larger ring illuminated when passing the OM. The other two, the MM and arriving at minimums??

Marker

A lot of people rag on the FCS-70 but I think it's a fine autopilot and actually flies the airplane better than the SPZ500. My 500 rental jet has the Bendix and with GPSS and WAAS, it will practically land itself. The boxes in the nose weigh about 20lbs each!!

Fun to learn something, I had no idea what those rings on the ADI were for.

But back to the door. If a triangle is the strongest shape and trapezoids are stronger than parellelograms; the Citation door is the closest you can get to a triangle and still be useful. I'm not an engineer but that's my best serious guess.

My guess:

An earlier post showed the structures in the fuselage, showing that the fuselage designers put a nice rectangle cutout for the door. If you were on the fuselage design team, you’d look at your work and say, yep, nice and symmetrical.

Then later the door design team is called in. They start trying to engineer a doorframe and door to fit into that square hole, to include a latching mechanism and seal. They are tying to design the best thing to fit into that fuselage hole they were given.

They need to make the latching mechanism fit, which means more structure and moving parts in certain areas. Can’t be a rectangle without over complicating the mechansms. After trying a few options, they decide the least-worst option is the taper and a smaller door at the top.

Someone asks the door design team why the door is tapered. “Because you gave us a rectangle hole to fill! If you want a rectangle door give us a tapered hole next time.”

Perfect. We should have to work for it, or wait for it.
Let the suspense build!

Actually IIRC Outer, Middle and Inner marker lights (blue , yellow, white)
Its been a lot of years. Even though there were chuckles when the Citation came out (Slowtation, claw marks on the wings from perching birds) I thought it did a good job for what it was designed to do.

Still waiting for the big reveal on the door



The larger ring illuminated when passing the OM. The other two, the MM and arriving at minimums??

Nearjet vs. fearjet. AD note to install chickenwire on back of Citation engines to keep birds from flying up the exhausts. Aways able to tell Learjet captain from FO by the way they leaned when they walked, ect., ect. However, there seem to be a lot more Citations than Lears, Hawkers, Sabres, ect., seen on ramps today.