I think on the real 737s (all models), the main gear retracts flush against the underside of the fuselage and the outboard tires actually fit snugly against the airframe to serve as a seal. There are of course no main gear doors as a benefit to this design. On the PMDG 737 visual model the main gear leaves a gap around the tire edges and fuselage when fully retracted. Might freeze our hydraulic lines at CRZ alt :), not to mention how uncomfortable wheel well stowaways would be (remember that story in the news, lol). Not trying to nitpick though, the visual model is otherwise flawless and I love it. I do get a charge though mentioning something like this and one of the PMDG guys comes back and gives me a :) face with the reply, 'it's been fixed in SU2'. Thanks.

Sorry that is not the case with the tires, it's the *over sized hupcap* that forms the seal. How this is on this aircraft is for vin to answer. IMO not a big deal compared to flying issues being fixed.............[h4]Best Wishes,Randy J. Smithhttp://img.villagephotos.com/p/2003-5/196432/winglets_lg.jpg

"Sorry that is not the case with the tires, it's the *over sized hupcap* that forms the seal."Isn't it a combination of both, Randy? The rubber blade-type seals (around the circumference of the holes in the fuselage) contact the tyres' outer diameter forming a seal... and the oversized hubcaps prevents air going into the wheel well via the ventilation holes in the wheel centre part(and also provide an aerodynamic fairing over the axle).However, modelling flexible seals would be difficult and probably not worth the effort ;-)Cheers.Ian.

"Might freeze our hydraulic lines at CRZ alt , not to mention how uncomfortable wheel well stowaways would be (remember that story in the news, lol)."Hydraulic fluid is ok from -65degF to 275degF, James... so I think they'd be ok ;-) As for the stowaways, there isn't a great deal of room in the 737 wheel wells, so I think their biggest worries would be, in chronological order...Falling out of the wheel wellGetting squashed by the gear as it is retractedPerhaps getting fried/burnt.... tyres, wheels and brakes can get really hot just from taxying (and taking off).Lack of oxygen, and...If they survived that... then they would have to worry about getting frozen in cruise ;-)Cheers.Ian.

Not too long ago someone actually did that, I think on a flight from the the Phillipines to somewhere in the US. May have been a 747 though, definitely not a 737. The person described hanging on for dear life during the gear retraction and extension sequence (as one can imagine). He was treated for hypothermia but apparently never lost consciousness throughtout any part of the flight.I'm not sure if he was granted a visa though :) What a crazy story. The next thing you know someone is going to claim to have mailed themselves in a big crate via airmail to their parents house across the country. :) (that actually happened here in the US a couple of months ago). The truth is stranger than fiction.

Rugerdog, ask yourself this question? Exactly what do you need a seal for?If there is to be a perfect "seal" when the wheel is fully retracted, then by putting a little thought into it, this would mean that part of the wheel would be scrubbing against the enclosure whenever the wheel is extended/retracted.What happens to the circumference of the tyre as it is utilised? Hint: what are those black marks that you see on the touchdown zone at the end of the runway. How is this seal going to be maintained over the life of the tyre? Over inflate?Not to mention that aircraft tyres are not a precise science so you are not going to get tyres that match inch for inch (millimeter for millimeter) - this would mean some tyres would be slightly too big.Oh yes don't forget flat spotted tyres!! How are those going to be sealed.Also factor in, is the oleo going to have the EXACT same extension everytime the wheel is retracted, to add a mechanism that ensures that this is the case is going to add to weight and complexity of the landing gear.What about expansion of the rubber on the tyres, airlines in hor countries are going to have a problem. On the ground the tyres are going to be hot. Get to cruising altitude the tyres are now cold, guess what - they contract - how is the seal going to be maintained then? It would mean that the enclosure would have to be self adjusting in order to maintain the seal - more mechanisms to add weight to the aircraft.What happens if for some reason the tyre where to explode, this would mean it would damage the part of the airframe that it was in contact with: 170 psi is a lot of force to contend with.The point I'm trying to make is that aircraft are not as complicated as you would feel. Trust me on this one, there is a gap between the tyre and the landing gear bay - well at least on the aircraft I have worked on - albeit recently they are much smaller than a 737 (i've done maintenance on lots of sizes, from Cessna 150 up to Boeing 747-400/Airbus A340).paNMan

See, I didn't know all this. I learn something new every day. Thank you for your very detailed and thorough explanation sir. When you put everything into perspective like this, the gaps actually look kinda cool, especially knowing now how the real aircraft works. :)

"Trust me on this one, there is a gap between the tyre and the landing gear bay - well at least on the aircraft I have worked on - albeit recently they are much smaller than a 737 (i've done maintenance on lots of sizes, from Cessna 150 up to Boeing 747-400/Airbus A340)."So you're saying that you haven't worked on a 737, Panman? Are you aware of the very robust flexible seal around the circumference of the cutout in the 737 fuselage?Quote from the 737NG Maintenance Manual:"There are no wheel well doors. The blade-type seals around the openings in the bottom of the main landing gear well make an aerodynmic seal around the ouboard tire when the main landing gear retracts""If there is to be a perfect "seal" when the wheel is fully retracted, then by putting a little thought into it, this would mean that part of the wheel would be scrubbing against the enclosure whenever the wheel is extended/retracted."This is why the seal is both flexible and robust. The main gear wheels are braked before they retract, so this prevents abrasion from spinning tyres. "What happens to the circumference of the tyre as it is utilised? Hint: what are those black marks that you see on the touchdown zone at the end of the runway. How is this seal going to be maintained over the life of the tyre? Over inflate?"The flexibility of the seal should accommodate this. It is several inches wide.I think you'd understand if you saw a photograph of the flexible seals... Unfortunately, I don't have one at the moment :(Cheers.Ian.P.S. Er... did I forget to mention the seals are flexible? :(

Cool Ian. I'd like to see a picture of those seals if you get a chance to upload it some time. Interesting stuff.

That's exactly what I said, never worked on em.

I assume that the seal you folks are speaking of is fairly clear to see in this picture?http://www.airliners.net/open.file/415574/L/Alan Liebowitz

Okay Ian, point it out to us :) Good picture though, wow. How the heck did the cameraman get in there?

The main gear bay is not as small as Ian makes it sound. hose tires are in the order of 3 feet tall :) That photo was taken standing in one side of the well looking ot the other. On the ground I could not touch the top of the well/cabin floor.I've been in the wheel well of a UAL-300 and the seals are essentially reinforced flexible rubber flaps. I would not be surprised if there was a bit of pressure delta between the wheelwell and the outside in order to keep the seal tight.Tim

"Okay Ian, point it out to us :) Good picture though, wow. How the heck did the cameraman get in there?"It's difficult to see the construction of the (black) rubber seals in this pic (at least on my monitor), but they are on the circular section in the lower half of the screen (jagged, overlapping). The thin grey seals, further away from us are for the "doors" (or rather the small sections of bent metal attached to the strut).I agree, the pic is very good. It's taken with the cameraman standing in the right hand wheel cavity, looking towards the left. It's easy to get in there, you just walk inboard of the gear (easier from the aft of the wing) and through the cutout in the fuselage (for the strut). Getting from one side to the other is a little harder... as you have to stoop down low (harder for some...e.g. tall, middle aged people ;-))The Standby Hydraulic system reservoir can be seen in the bottom left of the pic. The flap drive mechanism includes the green-painted, odd shaped device above/to the rear (left in pic) of the far side of the hole and the red/black striped rod on the aft bulkhead. In the top right hand corner of the pic you can see part of the Hydraulic Reservoir for System A.I think you'll find, James, as I did, that the 737 is not your typical Boeing. You can't assume anything about the 737. That is what I'm trying to get across, here ;-)Hope this helps.Cheers.Ian.

"The main gear bay is not as small as Ian makes it sound."Still, I wouldn't like to be sitting on the keel beam at V2 + 20 when those wheels came up :-) (And we do want to discourage stowaways as much as possible, don't we) ;-)"On the ground I could not touch the top of the well/cabin floor."On my tip toes, I can touch the cabin floor (with my hands), so it must be about 8' (I'm sure I'll be out there with my tape measure next time I'm at work).By the way, does anyone know what those two purple thingamies are in the bottom of the picture? They look like oversized electrical fuses.Thanks.Cheers.Ian.