No Wheel doors on 737s

[fredhoward]

If there are no penalties by way of drag, etc, for the lack of covers over the main undercarriage wheels on 737s, I wonder why Boeing (and others)haven't done it on other aircraft. The cost and weight savings must be immense.
Can anybody enlighten me, please ?
Thanks,
Fred

[barit1]

There is most certainly a drag penalty - but for the primary 737 mission it is outweighed by the other factors you mention.

But this begs the question - what about the BBJ and other long-range ops? Has this option (gear doors) been evaluated for cost/benefit for 3000+ mile legs?

[fredhoward]

Thanks for that, Barit. I've had all sorts of questions over the years but have not known how to find the answers. I'm amazed at the quick responses here, coupled with appreciation to the Authors of this site who immediately send me an email with a Url to the answering page ! This is quite a complex site and I'm not sure which section I've posted questions under, so that facility is a great help.
Fred

[Seat1APlease]

But this begs the question - what about the BBJ and other long-range ops? Has this option (gear doors) been evaluated for cost/benefit for 3000+ mile legs?
It is by no means a quick design change. As you know, if you watch an aircraft with doors take off, then first the doors fully open, then the leg retracts then the doors close again. It would need major changes for hydraulic lines door positions etc.
On the 737 series the main gear just hinges up sideways into the centre section. To go through such a major re-design on an aircraft as old as that would probably not now be economically worthwhile for the sector lengths it typically does, even the BBJ will not always be doing the long sectors every time.

[alexban]

I think there are also other benefits of not having those doors: for ex improved brake cooling ,or less chance for a stuck raised landing gear.
I think the drag penalty is very low, as I've seen the plane with the ldg gear raised,on jacks , and the gear fits very nice into the fuselage,and has some fittings around the wheels also.
The fuel consumption is similar with the Bus (using the same CFM engines), or even lower, maybe due to lower weight ,also.
Maybe ,on longer sectors, having those doors would be a plus.

[Mad (Flt) Scientist]

I wonder why Boeing (and others) haven't done it on other aircraft.

Some have. CRJs (and Challengers) have a similar arrangement to the 737 with the actual wheel forming the closure to the wheel bay. With regard to the cost/benefit issue of fitting the wheel doors, the GEXs do have doors to fully enclose the wheel bay - so (assuming the right decision was made to fit them) the range where it makes sense is somewhere between 3000 and 6000nm.

[grababadger]

The wheel hub caps are esposed to the airflow and follow a aerodynamic contour.

Extra form drag, although minus the weight of the doors and the actuators, valves and although minimal-savings in maintenance.

I think with new material's, composites, plastics etc-it will be less of a consideration.