After looking at AC 43-210A I'm thinking I can do a 172D patrol door mod as a minor mod to the aircraft, but I do intend to talk with the Seattle FSDO first to see if they consider modifying the bottom half of a (removeable) door a major design change. That being said, I'm wondering if anyone has a field approval to use as a reference or, better yet, an STC. I've drawn on blank on the STC so far.

Why?

Cary

The owner's a friend & asked me to do the mod for him. Guess he'd seen them on other Cessna's and liked the idea.

OK. I wondered, because I can't see the usefulness of them. Any windows in the lower part of the door are mostly blocked by the seats when they're slid forward to their normal positions, and the passenger side is completely blocked if there's someone sitting there. Bubble windows might be different--I've never flown in an airplane with them installed, but I've seen a number in several Cessna singles.

Cary

Would never have bubble windows. I leave the straps undone on mine so windows will open up in flight. Airflow holds window up on bottom side of wing. For taking pics or cooling off on a hot day.






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I'm a fan of the bubbles. Seems to add more cabin space.

Personally I have had two 185's with Patrol Doors. Coolest factory accessory ever. They do provide excellent downward vision on the opposite side of the aircraft, provided nobody is sitting there. When I am doing my work as a geologist, nobody is in the plane with me, so it is just fine. If you have a plane load, it gives the rear seat passengers a excellent downward and somewhat forward view.

As for making a set, good luck with that. I took some time in looking over the structure when I replaced the glass in the lower section. There is a ton of hand made and fitted spacers and structure. To make the door ridged a lot of small complicated structure is put in the remaining solid portion of the door to ensure its rigidity. The entire outer skin is custom and riveted all along the outer edge of the entire door and along the window. Heck, replacing the glass is not for the faint of heart. Don't think you just chop a hole in the middle of the structure and rivet a pice of plexiglass in the hole, it is not at all that simple. However, you could be an engineer of extraordinary talent and make a thing of beauty and strength. Good luck with it.

BTW, I to do the floating window trick. I do have to take off my window and replace it with a flat one, as I have bubble windows on my 185. The bubbles will float up as well, but have significant drag and over stress the hinges. There are airspeed restrictions on this trick, the hinges are not really that strong and the tabs will start cracking if you do not keep your speed low. While I was in the NOAA Corps, we modded our 210's right window, so it had a removable insert. Somehow we managed to make the hole the magical resonant size for the aircraft. It would do this intense low frequency beat that was almost painful and felt like the airframe would explode.

I like patroller doors, I wish my airplane had them.

I like the way patrol doors look, but agree with Cary that they seem to be mostly blocked off in a 4-seat Cessna
if someone's sitting in that seat, or if the seat is slid forward.
Used to be a guy on my airport with a Luscombe with a single RH patrol door, it looked odd but it had some utility.
Never thought about the back-seaters looking through the patrol doors on a 180/185, possible but seems like a stretch.

FWIW I've seen a Maule once with factory patrol doors, where the interior side of the door had been upholstered right over the view-port.
Got a good laugh out of that one, esp when I thought about what Maule probably charged for that extra.

hotrod180 wrote:I like the way patrol doors look, but agree with Cary that they seem to be mostly blocked off in a 4-seat Cessna
if someone's sitting in that seat, or if the seat is slid forward.
Used to be a guy on my airport with a Luscombe with a single RH patrol door, it looked odd but it had some utility.
Never thought about the back-seaters looking through the patrol doors on a 180/185, possible but seems like a stretch.

FWIW I've seen a Maule once with factory patrol doors, where the interior side of the door had been upholstered right over the view-port.
Got a good laugh out of that one, esp when I thought about what Maule probably charged for that extra.

We have done a couple of maules with patrol doors and then put on upholstery just for winter. Just snaps off in the summer. Very useful.
I would also prefer patrol doors over bubbles. I'm slim so I don't notice the extra room, and I can't get my head in them to look down, so the bubbles are useless for me.

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Really, back seaters in the 185 love them, ask the 200+ folks I've given rides to at Burning Man during the events. I don't sit back there as a rule, so I can't say fist hand but most of my riders raved about them. I get similar comments from folks that come visit and I give rides to over the Grand Canyon.

I think the back seat view might be the main motivation; the owner's kids ride in the back.

I don't think I'll have a problem with the physical/mechanical aspects of building a patrol door for the 172D, but I hadn't given enough consideration to resonance. Very good point, and I appreciate the anecdote concerning the 206. There's no replacement for first-hand experience. The aircraft is approved to fly with the doors off so it has quick-release pins in the hinges. Sourcing/procuring a second door for the mod or using a second door as a guinea pig might be the way to go, swapping doors would be easy. At the very least using a second door would save some painting headaches if the modification didn't work out as hoped.