Burning Question (737)

[Zomby Woof]

Why is it, in all the pictures I've ever seen of any version of the 737,
that Boeing STILL doesn't cover up the main wheels?

Maybe the latest model (-800?) does...if so, I stand corrected.

ZW

[Csa751]

If it ain't broke, why fix it?

[John Hilt]

On 05 Oct 2003 03:41:06 GMT Csa751 wrote:

>If it ain't broke, why fix it?

It may be broke, but never admit it:

<http://www.pulitzer.org/year/1997/beat-reporting/works/737-4/>

When jets crash: How Boeing fights to limit liability

The potential costs to a manufacturer are enormous if its product is
blamed for deaths and injuries: millions of dollars to victims and their
families, many millions more if a product must be recalled and fixed,
and the incalculable cost of a damaged reputation.
_______________________________________

Say no more ...

--
_/_/_/ -=jh=-

[CSA722]

All that because they don't want to put gear doors on where they're not needed?

[Zomby Woof]

Then why bother putting gears doors on ANY aircraft?

What singles out the 737?

ZW



"CSA722" > wrote in message
...
> All that because they don't want to put gear doors on where they're not
needed?

[Csa751]

What difference does it make? It works. Many older recip aircraft didn't have
doors that completely covered the gear. The 737 is just the only jet. (that I
know of). It allows more useable space above the gear wells and is lighter. The
increase in drag doesn't appear to have affected it's performance enough to
matter to the hundreds of operators and there's several less parts to cause
trouble, cost money and decrease reliability. Sounds like a win win situation.

[Robert Moore]

"Zomby Woof" wrote
> What singles out the 737?

Although my experience is only in B-707 and B-727 aircraft, one
of the problems that I encountered when doing short-haul operations
in them, was that of brake over-heating. A problem that was
addressed in the Aircraft Operating Manuals and was dealt with by
leaving or putting the gear down longer than normal. Since the
B-737 was intended solely for these types of operations involving
frequent TO and LDGS, short turn-around times and long taxi routes,
perhaps Boeing felt that leaving the wheels uncovered would assist
in the brake cooling problem.

Bob Moore
ATP B-707 B-727
PanAm (retired)

[Larry Fransson]

On 2003-10-05 20:15:11 -0700, Zomby Woof said:

> ?Then why bother putting gears doors on ANY aircraft?
>
> What singles out the 737?

Nothing. The straight wing Citations don't have fully enclosed landing gear either.

[John Hilt]

On Mon, 06 Oct 2003 12:54:09 GMT Robert Moore wrote:

>Since the
>B-737 was intended solely for these types of operations involving
>frequent TO and LDGS, short turn-around times and long taxi routes,
>perhaps Boeing felt that leaving the wheels uncovered would assist
>in the brake cooling problem.

I don't think so. There's plenty of time for brake cooling during turn
around and the following flight and approach. Just put your hand into a
200 - 270 knots air flow and feel it. :-)

Brake temperature is only critical just after landing. That's why
the wheels hubs on a Concorde are equipped with fans that run during
ground stops. Not exactly a short hop aircraft.

--
_/_/_/ -=jh=-

[Robert Moore]

John Hilt wrote
> Brake temperature is only critical just after landing. That's
> why the wheels hubs on a Concorde are equipped with fans that
> run during ground stops. Not exactly a short hop aircraft.

From my B-707 Flight Manual:

MAXIMUM LGW FOR SHORT TRANSITS
Takeoff must not be scheduled less than 40 mimutes after
any landing in which the gross weights and operating
conditions critical for wheel fusible plug melting energy
levels have been exceeded. See chart in section.........


Bob Moore

[John Hilt]

On Tue, 07 Oct 2003 13:46:01 GMT Robert Moore wrote:

>> Brake temperature is only critical just after landing. That's
>> why the wheels hubs on a Concorde are equipped with fans that
>> run during ground stops. Not exactly a short hop aircraft.

>From my B-707 Flight Manual:

>MAXIMUM LGW FOR SHORT TRANSITS
>Takeoff must not be scheduled less than 40 mimutes after
>any landing in which the gross weights and operating
>conditions critical for wheel fusible plug melting energy
>levels have been exceeded.

Well, the 707 is a pre-historic aircraft, and wheel fusible plug melting
energy levels are usually not exceeded during a landing.

--
_/_/_/ -=jh=-

[Simon]

Having flown the B737, and several of its variants, and been an FE on the
727, brake energy is a consideration. Long runways reduce that need, however
short runways with heavy load factors can overheat the brakes. The problem
can surface in two places. One is on the ground, and the explosion can kill
those nearby. The other problem is in the air and happens some 20 mins after
takeoff. The accumulated heat can, and has, caused a wheel well explosion.
In particular a B727 over Mexico a number of years back. There is a brake
energy chart, and for most slow turn arounds, it is usually a non issue.
Short runways, heavy loads, and quick turnarounds raises the risk.
Additionally, the other points that have been made about parts, weight, and
so on are also valid. BTW the A320 et al series also have brake cooling
fans, however they are only used over a certain temperature. Leaving the
gear down after takeoff is not an option for cooling the brakes. The brake
energy chart is what is followed. Leaving the gear down after takeoff (and
it is done sometimes) to cools the wheels violates the takeoff criteria.
With the gear down the aircraft does not meet the climb gradients on an
engine failure.

I would suggest that there is probably no one single reason the 737 has
exposed main wheels, but many. And probably Boeing has some idea what it is
doing.

Simon

[Larry Fransson]

On 2003-10-08 21:41:30 -0700, (null) said:


> Well, the 707 is a pre-historic aircraft, and wheel fusible plug melting
> energy levels are usually not exceeded during a landing.

The 500-series Citation is considerably less prehistoric than the 707, but brake energy is a serious consideration. During checkrides, we had to sit for a good 15 minutes or so (consulting the brake energy chart for the exact time) after a full stop landing before we could take off again. The company learned the hard way on that one, one time doing a full stop followed by an abort and then melting the fusible plug. It's not difficult to imagine getting into similar trouble in real life operations.

--
Larry Fransson
Seattle, WA