DC-10-30/-40 ops w/o center MLG

[barit1]

I have seen JAL DC-10-40's dedicated to short haul with the center MLG retracted (or perhaps even removed). What were the pros/cons/special restrictions of this sort of operation? I assume the MTOW & landing GW were reduced - what else?

[CV880]

I don't know the specific weights but there was a reduced MTOW with the CLG retracted. There was a guarded selector switch below the landing gear lever in the cockpit that allowed the pilots to select the CLG OFF before putting the gear lever DOWN. This switch shut off the hydraulics to the CLG and rearranged the landing gear warning and indicating systems accordingly. Since this was all in the Flight Manual some airlines used this procedure to reduce landing fees at airports where full MTOW was not required on the subsequent TO. There was a Maintenance Manual procedure to lower and lock the CLG down on the ground if it was required after landing with it retracted. Also it could be retracted (by maintenance engineers) on the ground for a 2 engine ferry for example.
Douglas also offered a DC10-30 variant with the CLG removed for hot/high operations and I think Mexicana might have taken this model.

[barit1]

Douglas also offered a DC10-30 variant with the CLG removed for hot/high operations and I think Mexicana might have taken this model.

It was called a DC-10-15. Both Aeromexico and Mexicana bought it, IIRC.

I'm not really sure if it was a DC-10-10 w/ CF6-50 engines, or a light-weight series 30 - but it was some kind of hybrid. Less than a dozen built, I'm sure.

[JW411]

The DC-10-15 was a DC-10-10 with DC-10-30 engines.

Fred Laker came up with the wheeze of using his DC-10-30s on short routes with the centre gear retracted in the hope that the landing fees would be based on the DC-10-10 landing weights.

It didn't work though for everyone charged on the max landing weights for the individual aircraft concerned; ie DC-10-30 landing weights (403,000 lbs if my memory serves me right).

The other problem was that some crews forgot to lower the leg before landing back at LGW and this used to p*ss the ground crew off something rotten for they had to jack the aircraft up to get the centre gear down and locked.

After a short period we forgot all about the idea of isolating the centre leg.

However, I remember later in life when working for a Far East company that we had a deflated tyre one night at Seeb. We were able to pinch one off the centre gear and fly back to base as a DC-10-10!

[CV880]

I was told Air New Zealand used this procedure with their DC10-30's on their services across the Tasman to Australia toward the end of their life at ANZ but obviously an agreement had to be in place with the revenue collectors to get any benefit from it.
The DC10-30 without CLG was offered to Cathay Pacific in the early 70's on the basis the CLG could be added later and the Flight Manual revised if long haul services were introduced. CX opted for the L1011 in the end.

[Golf Charlie Charlie]

Is it true that the A340 (I guess only series -200 and -300) can also be configured to operate without the centre gear ?

[Doctor Teeth]

A340-300 can operate with the Centre Gear inop in the retracted position with the MTOW restricted to 230,000KG and the MLW restricted to 185,000 KG.

[Engineer]

The weight restrictions with the centre gear retracted are:

MTOW 199.6T
MLW 164.9T
MZFW 158.8T

The MTOW is approximately the same as a -15 (204T). So with it retracted the aircraft performance is similar to a -15 (-50C2R engines) as opposed to a -10 (-6 engines).

But with MTOW reduced by 67T this is a huge penalty for long haul operations :{ But :ok: for short haul

No other restrictions apply except in the event of a dual hydraulic failure, involving the landing gear system, consideration would be given to maintain the centre gear retracted.

Merry Xmas

[CV880]

JW411,
I thought the procedure to lower and lock the CLG on the ground required maintenance to partially lower it using the aircraft electric hydraulic pumps and the CLG selector valve in the RH wheel well, then deflate the strut, complete the extension and downlock, then reinflate the strut to the required pressure. Retraction on the ground was the reverse process. No jacking required? Never did it myself but saw the results of not following the AMM when PAL were retracting the CLG in preparation for a 2 engine ferry back to MNL with a failed N0.3 engine and they did not deflate the CLG strut before commencing retraction. The CLG retract actuator broke/bent and dumped all no. 3 hydraulics on the ground.
Happy New Year

[LEM]

I remember seeing an Alitalia MD11 with the center gear "inhibit" pb safetywired, by fear of pilots landing by mistake without it at high weights...