FedEx Burns Another
Safety Lessons from the Latest Accident of a FedEx Aircraft
Air Safety Week 08/07/2006
It's been an article of faith among multi-engine pilots that if you
drive your bird in a little hard, forget to flare or kick off the drift,
then all that will happen is that touchdown will feel significantly
different, a few fuel-tank seams might weep tears of fuel, and the
engineers might rib you for causing them extra work.
Of course, you will have admitted your sins to them, written up the bird
and waited anxiously while they carry out a heavy landing inspection.
That check will progressively indicate, item by item, whether you've
permanently bent anything, or whether they need to check more deeply
because of what they've found. Most of the time, you will not have bent
anything and the procedure is quite perfunctory. It could happen that
you've bottomed out the oleos and witness-marked an indicator. Rarely
will a heavy landing blow or even scrub a tire, let alone damage the
gear or airframe.
After the latest FedEx MD-10 burning on runway 18R at Memphis, Tennessee
on July 30, the company's pilots might be forgiven for surrendering up
the above article of faith. In fact, they may be pondering why their
"Mad Dogs" are so lame that their legs collapse at will. FedEx pilots
are made of sterner stuff, so they will just take it on the chin and
polish their landing techniques, making sure to properly adrenalize
before each and every landing. "Failure is not an option" I seem to
recall someone famous saying, while baying at the moon. Evidently the
Mad Dogs 10 and 11 never got that message. They appear to be
particularly weak-kneed.
It Seldom Happens In the latest accident, the left landing gear failed
on the airplane during landing, sending sparks into dry grass beside the
runway that ignited a fire. Three people on board used an emergency
landing chute on the right side of the plane to safely escape, avoiding
the burning engine on the other side. Fire crews responded quickly and
doused the fire with foam, containing it to the engine area and
preventing it from spreading to the rest of the aircraft. The plane,
identified as FedEx Flight 630, had departed from Seattle, Washington.
Les Dorr, an FAA official in Washington D.C., said landing gear failure
is a rare occurrence. "A landing gear collapse on a large transport-type
aircraft is a pretty rare event," Dorr said. "It seldom happens."
The MD-10 was a valiant attempt by FedEx/MD (and then MD's takeover
merchant Boeing) to use up the remaining life in the plentiful old DC-10
airframes by upgrading the cockpit to an MD-11 style two-man standard,
simultaneously rewiring and freighter-converting it. Like the two-man
MD-11F operation, it promised to be a very economical long-haul
freighter. The DC-10-10 had a Max Gross Weight increase to 446,000lbs
and the DC-10-30 to a massive 580,000lbs in the Series 30 MD-10. That
boost in cargo-carrying capability required "structural changes".
The Advanced Common Flight Deck was intended to allow FedEx pilots to
operate either the MD-10 or MD-11 interchangeably, for maximum
scheduling efficiencies. However, when the FedEx pilots got their hands
on the MD-10, they protested vociferously. They considered that there
were sufficient dissimilarities as to make any dual qualification
unsafe. Unlike the 757/767 and the A340/A330 combos, the MD-10/MD-11
basic designs and handling qualities were of two entirely different
eras. The company didn't agree and the FAA and Boeing backed FedEx, so
the pilots got to operate both. One wonders whether the Flight
Operations Quality Assurance (FOQA) program has since disclosed any
lingering safety interludes for those who fly both, interchangeably.
FOQA regularly checks data-recorders for any pilot handling quirks that
would be better if they were ironed out with counseling or added
training. One could also speculate as to whether any such handling
difficulties, particularly the touchdown, might have carried over into
longer term aircraft fatigue damage. The MD-11 has had to undergo a
number of flight-control software patches in an attempt to cure it of
some of its near-the-ground vices. It is reportedly very unforgiving of
a one gear first hard touchdown, as the pilot of a Mandarin Airlines
passenger flight found on his arrival in Hong Kong on the night of Aug.
22, 1999.
Turning Turtle That aircraft lost its right gear and wing, inverted and
caught fire, killing 3 passengers.
The pilot had disconnected the autopilot but left the autothrottle
engaged, which failed to compensate for the gusting crosswind. An
amateur video showed the aircraft's quite normal approach in turbulent
conditions, followed by a high-rate descent beginning at around 50 ft RA
(radar altimeter). Wind-shear had caused a sudden loss of around 20kts
and the autothrottle failed to respond. That was the height it was
software-scheduled to throttle-close for the flare (or landing
round-out).
Near to max landing weight, and in an unremarkable less than 4 degree
right wing down attitude (for the crosswind), the aircraft hit with a
high rate of descent. This allowed the RH oleo to bottom out, the #3
engine to touch the runway and break off, taking the RH wing with it.
Looking at the relative positions of the wing-gear and the engines
(further outboard), it's not surprising that the weight of the engine
should allow its downward inertia to lever the wing off above the gear
in a hard touchdown.
It's this lack of robustness that gives the MD-11/MD-10 its undoubtedly
unique characteristic, for a wide-body, of being able to shed a wing and
achieve an inverted attitude on the ground. Other MD-11 pilots expressed
surprise that an experienced MD-11 driver would have left the
autothrottle engaged in these conditions. Most had found that the
programmed throttle closure in the flare could often, as in this case,
prove to be the opposite of what conditions (particularly rapid onset
wind gusts) demanded. The only other available solution for arresting a
high-rate descent near the ground is backstick. Unfortunately in the
MD-11, that means an automatic hard tailstrike and a million dollar
damage bill. Pilots are taught to freeze the pitch attitude and "fly
out" of any high rate descent near the flare with added power. That
might kill the speed bleed and extend the landing roll but it precludes
the tailstrike. In the Mandarin case, with a nasty wind-shear, the
throttles auto-closing at just the wrong moment and the pilot
pre-programmed NOT to use backstick, the accident deal was already
closed.
On Dec. 21, 1992 a Martinair DC-10 PH-MBN touched down hard in gusty
conditions at Faro, Portugal. It was again a right gear first touchdown
-- and the wing separated. On July 31, 1997, a FedEx MD-11F touched down
hard at Newark, New Jersey with a 500 ft/min descent rate and a slight
right bank. The right wing-spar broke and the aircraft ended up on its
back, burning. The finding was that the landing was over-controlled and
a go-round should have been carried out. On Dec. 18, 2003 it happened
again, to an MD-10 at Memphis on runway 36R, after a quite stable
approach. A young F/O never quite got the drift off and touched down
firmly on the right gear with a very slightly banked attitude. The RH
gear collapsed and the aircraft burnt out. The NTSB faulted the pilot
and the flight captain, who was also a check and training pilot. The
company changed its training regimen after that accident.
The common denominator for the generic DC-10 and its spawned sub-types
would seem to be an underbuilt wing that allows a coupled engine
inertia/main-gear response to break the wing or gear-mounts, in any
slightly wing-down, harder than normal arrival. When combined with the
aircraft's heightened pitch sensitivity and the
MD-10-10/MD-10-30/MD-11F's quirky differences, it would seem that a
FedEx pilot goes frequently in harm's way and must work harder than most
to "keep it all together."
