737NGX

737s presently have aerodynamic seals which meet with the tyre walls to create a fairly smooth surface when the gear is retracted, but the landing gear on the 737 prototype did originally have main gear door seals which were far more complex, however, these were not doors in the conventional sense, instead they were a set of inflatable door seals which were operated by bleed air from the engines.There was a switch on the main panel near the landing gear lights labeled 'Gear Seal Shutoff', this was so the air being supplied to the pneumatic gear doors could be cut off if the inflatable seals had a puncture (since it would otherwise have been wasting bleed air). You could tell if that was the case because there was an additional landing gear annunciator light which had a 'Not sealed' caption on it, and this would indicate if there was a leak in the system. Boeing dropped the idea of inflatable door seals because the inflatable seals were not really so much better than the simple ones which it has these days, and the addition of another system would have meant further maintenance and expense.Al