Easyjet B737 pitch-down incident 12 January
 

Anyone know any more about this from the NTSB website - sounds pretty serious. NTSB Identification: DCA09WA023
Scheduled 14 CFR Non-U.S., Commercial operation of easyJet
Incident occurred Monday, January 12, 2009 in East Anglia, United Kingdom
Aircraft: BOEING 737, registration: G-EZJK
Injuries: 4 Uninjured.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.
On January 12, 2009, at 1545 Coordinated Universal Time, an easyJet Boeing 737-73V, registered in the United Kingdom as G-EZJK, experienced a violent pitch down during flight. Vmo was exceeded by 100 knots, and a 10,000 foot loss of altitude occurred. The aircraft recovered from the maneuver and landed safely. 4 flight crewmembers were on board, and there were no passengers. None of the flight crewmembers were injured.

The investigation is being conducted by the United Kingdom's Air Accidents Investigation Branch (AAIB), and the NTSB has designated a U.S. Accredited Representative to assist the AAIB in their investigation.

"Vmo was exceeded by 100 knots, "

If true this is serious and shows boeing aircraft are built like tanks.

I believe this happened during a post maintenance (end of lease) test flight out of Southend.

I believe something similar (but I think a bit less dramatic) happened on a post maintenance test flight to one of Ryanair's fleet.
One of the procedures involved ( if memory serves me well) involved disconnecting all hydraulic power to the controls in flight. If the rigging or stab position ( well something of that nature, need an engineering bod to confirm) had been misset ,the result was ,in that case ( and possibly here too) a fairly violent pitch down.
I was told by the Capt concerned it certainly gained their attention, and very importantly that of the Ryanair engineering bod on the jump seat. ( Unfortunately fo him he paid the price for his FLS colleagues gashness :D )
As discussed on other threads, " would you like to take the airframe up immediately post maintenance ? " NO THANK YOU :=

Disconecting hydraulics to the flight controls is called a "Manual reversion" test. It allows you to fly the aircraft without hydraulic power to your flight controls. Its an emergency procedure for hydraulic failure.

c24

Remember the TNT 737 that "touched" down at EMA and then BHX back in 2006? Definitely tank like.

Just as solid as a Tu-154!!!!

cessna24, with 12500hrs on 737 I know what manual reversion is.
What I refer to was a procedure not dissimilar to the scenario you would find yourself in with loss of hydraulics, but was required specifically after a control surface had been repaired/removed,and, if I remember correctly, also involved switching the guarded overhead switches off too .It was I suppose, intended to give a scare when you might be half-expecting it rather than following hydraulic failure some years later.

EZY statement
 

EZY has given the basic details: EasyJet Boeing 737 plunge being investigated by AAIB and NTSB

The AAIB is apparently silent on the matter despite NTSB opening up at least the simple facts.

B737 pitch down during test flight. Hand-back to leasing co.
 

From Flightglobal.com

The US National Transportation Safety Board says it is assisting the UK Air Accidents Investigation Branch in a probe of a "violent" pitch-down by a Boeing 737-700 (G-EZJK) during a non-revenue flight over East Anglia, UK, on the afternoon of 12 January.
According to an NTSB preliminary incident report, the 737 was carrying four flightcrew members only when a "violent pitch down during flight" occurred. Though the pilots had recovered the aircraft and landed normally, the aircraft had exceeded its maximum operating speed (VMO) by 100kt (185km/h) and lost 10,000ft (3,000m) of altitude during the event. No-one was injured. The NTSB says the figures it has provided are subject to confirmation.
In a just-released statement: “EasyJet can confirm that we are working with the AAIB regarding an occurrence over the North Sea involving EasyJet test flight, EZY8010 from Southend to Stansted - which diverted to Southend, on the afternoon of 12 January 2009.
We can also confirm that the only people onboard the aircraft were the Captain, the First Officer and two observers. The Boeing 737-700 was being tested as part of the hand-back procedure to its leasing company.
Unfortunately, at this stage we can not provide any additional details on the occurrence as we are collaborating with the AAIB”. The AAIB has not yet responded to questions on the event.

Manual reversion
 

That particular check is a test to see whether the balanced anti-balance (servo) tab on one of the elevators is doing its job correctly. This could very well be what they were doing as it is part of the Boeing approved acceptance test curriculum. The reason this tab is there is to provide some alleviation of the control forces in case of a total hydraulic failure.
If the linkage connecting the tab to the elevator and horizontal stabilizer is adjusted wrongly it can potentially result in a violent pitch-up or pitch-down when the hydraulics fail or are manually switched off, because the tab will start to move the elevator to an aerodynamically neutral position, much like a trim tab on smaller aircraft, except of course for the fact that this one can't be adjusted in flight. Where this neutral position is relative to the stabilizer, is defined by how the adjustable linkage is set on the ground. This job requires some extremely precise work.

If the report of 100 knots above Vmo is correct, what would that mean for the future of the airframe? What tests / inspections would be needed to determine if any damage had been done?

...and I'm sure the leasing company are a bit peeved!

100 Knots above VMO is a significant exceedance, I do not fly the 737 but have jumpseated a few times and would guess that would work out to about 430 kias.

I would think this would exceed even manufacturers / airworthiness testing VD ? by a major factor.

Would be interested to see how the airframe held up :eek:

NWSRG asks
 

The following is an extract from a Boeing maintenance manual (not 737 but very similar type and checks will also be very similar). Its a bit lengthy but by no means complete It is also edited/cropped as well. Just skimming through should give you a very good idea of just how they go about such inspections.
You can see from the inspection title, it actually covers several conditions and not just Vmo/Mmo exceedance. I have left in the paragraph defining severe turbulence just for interest as this topic is also debated frequently on here at times.


MAINTENANCE MANUAL

SEVERE OR UNSUAL TURBULENCE, STALL BUFFETING, OR EXCEEDING DESIGN SPEED CONDITION-MAINTENANCE PRACTICES (CONDITIONAL INSPECTIONS)


1 . General
A. The structural examination in this subject is applicable after a severe
or unusual turbulence or buffet condition. It also applies to stalls
(after the initial buffet or stick shaker condition), or if the airplane
speed is more than the design speed.

(a) The pilot must make a decision if a structural inspection is
necessary.

Note: If an inspection is necessary, refer to the "Examine the
Airplane Structure" in this section.

Note: Severe turbulence is identified as turbulence which
causes large, abrupt changes in the altitude and/or
attitude. The airplane could be out of control for
short periods. It usually causes large variations in
airspeed. Passengers and crew are moved violently
against their seat belts


C. The data that follows applies to airplane speeds greater than the design
speeds:
(1) The maximum design speed of the airplane for usual flight operations
is the Maximum Operating Speed. The Maximum Operating Speed is
found in Section 1, LIMITATIONS of the airplane Flight Manual. The
aural warning horn will operate at this speed condition.
(2) If the airplane speed is 20 knots, or more than the Maximum
Operating Speed (20 knots above Vmo or 0.02 mach above Mmo), do the
Examine Airplane Structure procedure in this section.




MAINTENANCE MANUAL
(c) AIRPLANES;

Examine the fuselage, section 46 lower lobe for distortion,
paint that has flaked, and for cracks. Also look for fasteners
that have pulled out or are not there.

Note: A light skin wrinkling/buckling of the lower aft body
(between stations 1370 and 1470, below stringer 20L) is
a usual condition when the airplane is on its landing
gear. But, an apparent increase in the magnitude of
these buckling patterns is cause for more internal
inspections. This is shown by the formation of sharp
creases that usually show between the fasteners.
(d) Examine the complete empennage, section 48 for distortion,
paint that has flaked, and for cracks. Also look for fasteners
that have pulled out or are not there.
(e) If any external damage is found, do the step that follows:
1) Examine all of the internal primary structure in the
damaged areas. Look for distortion, paint that is flaked,
for cracks, and for fasteners that have pulled out or are
not there. Wrinkles in the keel beam vertical web are
normal.
(f) Examine all of the internal structure of the fuselage, section
48 that you can get access to. Look at the structure from the
rear pressure bulkhead to the aft end of the airplane. Look
for distortions, paint that has flaked, and cracks. Also look
for fasteners that have pulled out or are not there.
1) Look at areas that follow:
a) The aft fuselage bulkheads
b) The fin attach fittings
c) The horizontal stabilizer center section
d) The stabilizer hinge fittings
e) The stabilizer jackscrew-mechanism mount fittings and
support structure
2) Look at the jackscrew and hinges for signs of binding.
3) Inspect the horizontal stabilizer-to-body rubstrips. Look
for signs of movement of the structure against the
rubstrips. Such movement shows distortion of the
structure.
(g) Examine the external surfaces around the top and bottom
wing-to-body attachment. This includes the wing to body
fairing, and the rear spar web. Look for distortion, cracks,
badly chafed areas, and fasteners that have pulled out or are
not there.
(h) If external damage is seen, examine the body-to-wing joints,
and the landing gear beam-to-body joints. Also examine the
upper-wing skin splice for distortion, paint that has flaked,
cracks, and for fasteners that have pulled out or are not
there.

MAINTENANCE MANUAL
(i) Examine the external surfaces of the wing at the skin splices.
Look for misalignment and for rivets that have pulled out or
are not there.
1) Examine the external surface of the top of the wing
trailing edge for buckles in the skin.
2) If external damage is found, do the step that follows:
a) Examine all of the internal primary structure, in the
damaged area, that you can get to. Look for
distortion, skin that has buckled, cracked, and paint
that has flaked. Also look for fasteners that have
pulled out or are not there.
(j) Examine the wing control surfaces and the attachments at the
front and rear spars. Look for cracks and for rivets that are
pulled out or are not there. Also look for signs of binding.
1) If external damage is found, do the steps that follow:
a) Examine the spars for distortion, buckling, cracks, and
paint that has flaked. Also look for fasteners that
have pulled out or are not there.
b) Examine all of the internal primary structure in the
damaged area you can get to. Look for distortion,
buckling, cracks, and paint that has flaked. Also look
for fasteners that have pulled out or are not there.
(k) Examine the landing gear doors and landing gear uplocks for
damage.

S 212-011
(4) Examine the inspection and blowout doors on the lower surface of the
wing and the engine pylons. Also examine all inspection and access
doors on the lower side of the airplane body. Look for distortion,
displacement, broken latches, skin cracks and delaminations. Also
S 212-012
(5) Examine the wingtip fairings for distortion, cracks, and paint that
has flaked. Also look for fasteners that have pulled out or are not
there.
S 212-022
(6) Examine the horizontal stabilizer external surfaces for signs of
buckling. Look at the skin splices for cracks and fasteners that
have pulled out or are not there.
(a) If external damage to the horizontal stabilizer is found, do
the steps that follow:
1) Examine the spars for distortion, buckling, cracks and
paint that has flaked. Also look for fasteners that have
pulled out or are not there.
2) Examine the internal primary structure in the damaged area
you can get to. Look for distortion, buckling, cracks and
paint that has flaked. Also look for fasteners that have
pulled out or are not there.
(b) Examine the horizontal and vertical stabilizer rear spar webs.
Look for distortion, buckling, cracks, and paint that has
flaked. Also look for fasteners that have pulled out or are
not there.
(c) Examine the elevator external surfaces for cracks, fasteners
that have pulled out or are not there.
(d) Examine the elevator hinge bearings for signs of binding.
(e) Examine the elevator actuator bearings for signs of binding.
(f) If any external damage to the elevator is found, examine the
front spar web. Look for distortion, cracks, paint that has
flaked, and fasteners that have pulled out or are not there.
(g) Examine the fin external surfaces for signs of buckling. Look
at the skin splices for cracks, and fasteners that have pulled
out or are not there.
(h) If external damage to the fin is found, do the step that
follows:
1) Examine the internal primary structure in the damaged area
you can get to. Look for distortion, buckling, cracks, and
paint that has flaked. Also look for fasteners that have
pulled out or are not there.

Etc.etc

A-FLOOR,
Thanks for the clarification, that is exactly the one I was thinking of. As you say it "requires" some extremely precise work. My colleagues found out the results of imprecision.
Stilton,
That would be 440kias, think that would indeed be above VD by some margin.
Bloody impressive that they make them so tough, and I would think a fairly sterling bit of piloting to recover from that without overstressing the airframe.
A bit too close to an XL/AirNZ - plane plunges into sea on test flight -scenario for comfort.
Hope that check was indeed the cause, anything else (runaway stab) should have been nipped in the bud a bit sooner.

737 Manual Reversion
 

You can usually expect some pitching motion when disconnecting the hyds and there are limits of the number of units of +/- elevator trim to trim out the control forces that decide whether it is a pass or a fail for the test.

If I remember correctly, paint and balance of control surfaces does not require manual reversion flight test as suggested further up. The most common reason for calling a manual reversion test is replacement of the elevator trim tab control rods or the bearings on the tab brackets. This is a common occurence on major maintenance checks.

When the manual reversion fails on the flight test, the aircraft maintenance manual has a table that converts the number of units of trim required to the number of threads to adjust the control rod eye-end and hence rod length.

I have seen a very similar occurence to how this one is described when the elevator tab rods were adjusted following a failure of the manual reversion test on the initial flight test and the engineers carrying out the adjustment turned the eye-ends in the wrong direction. When the aircraft came back from the second flight test there was definitely a funny, not too pleasant, smell in the flight deck.

IF (repeat IF) tab rod adjustment is the cause of this occurence, I would doubt that the aircraft went into Southend for maintenance with this as an existing fault that has lain dormant until a manual reversion test was called on the hand back flight test. :(

My dad was an 'erk' (groundcrew) in the Far East during WW2. After the war had ended and things were a little less frenetic they spent a lot of time giving war-weary aircraft a thorough going over.

The pilots would always make the ground crew come up with them on the first flight after the overhaul. "If I'm going to prang, you're coming down with me." (Obviously not with Spits etc).

Dad loved it and logged many pax hours pottering over the jungles of Malaya and Burma. :ok:

I can only imagine how that must have felt for the crew. Hats off to them, the recovery from such an exceedence cannot be easy.

Out of interest, can anyone confirm what sort of altitude block is usually requested from crews during test flights in UK airspace? If they were over the North Sea I am assuming they were in controlled airspace at the time. Losing 10,000ft must be quite an experience:ooh:

Manual reversion test on the 737 call for an altitude of 36000 feet. So block of airspace requested 33000-39000.
Two types of trim tab rods..aluminium or titanium , the trim limits are different for each.
Hyds are switched off, pilot tries to maintain altitude and you count the trim wheel turns to null any pitch up or down tendency.
Complicated by the "slack" in the cable system......trim wheel may have up to 3/4 turn before any effect.

.. a violent pitch down exceeding 100 knots past it vmo loosing 10,000 ft altitude.. cant imagine how frightening that must have been for the flight crew..

Hats off the the flightcrew for recovering from such a violent upset:ok:

And there's me thinking it was just Airbii that bucked like broncos:E:E