www.skybrary.aero. B737 tail strike incident

[Centaurus]

http://www.skybrary.aero/bookshelf/books/3005.pdf

Not quite sure if this link to Boeing 737 tail strike incident extracted from SKYbrary Aviation Safety (http://www.skybrary.aero) is permitted by the Mods - but I hope so because it is a very interesting incident. It involves the case of a low hour first officer as PF and subsequent tail strike during departure. This was later compounded by a crew balls-up with later pressurisation selections which resulted in passengers complaining about hurt ears.

[SIUYA]

Centaurus...

Very similar event here in Australia in 2004.

Investigation: 200403868 - Boeing Co 737-86Q, VH-VOF (http://www.atsb.gov.au/publications/investigation_reports/2004/aair/aair200403868.aspx)

[chimbu warrior]

A possible contributing factor to the Spanish an Perth incidents is the application of excessive aileron during the rotation (mentioned in the ATSB report).

This would appear to have its origins in sim training, where some instructors (not Centaurus) encourage the application of full aileron to counter-act the effects of a crosswind. On the B738, any more than 2.5 units (as per the scale on the yoke) will result in spoiler deployment. This is discussed in the ATSB report.

Quite apart from the tail-strike risk, spoiler deployment during the takeoff roll is unwise on a short runway (Ballina, Sunshine Coast, Coffs Harbour etc).

[Centaurus]

where some instructors (not Centaurus)

Glad you said that.:ok:

I wonder how many similar incidents (crosswind handling) like this go un-reported? Possibly, a significant number.
I well recall a story from a colleague flying 737's with a new domestic operator in Australia. They departed from Melbourne Runway 27 with a 10 knot crosswind from the north. The captain, a former Ansett pilot, started the take off run with almost full aileron applied into the wind. Approaching V1, the acceleration rate noticeably slowed and the take off run was extended so much that the first officer had momentary doubts that the aircraft would get off before the end of the runway.

The captain was seemingly unperturbed apart from blaming what he said was a probable hidden tail wind component. In fact the reduction of acceleration was almost certainly due to excessive control wheel position during the length of the take off roll causing increased spoiler drag made worse at the higher speeds.

The Boeing 737 FCTM includes the following advice:

"Excessive control wheel displacement during rotation and liftoff increases spoiler deployment. As spoiler deployment increases, drag increases and lift is reduced which results in reduced tail clearance, a longer take off roll and slower airplane acceleration".

During airline simulator training it is still common to observe pilots persisting with unnecessarily large control wheel inputs at the start of and during the take off run; even though any crosswind is negligible. This may be the result of former early flying school training particularly in high wing types that have relatively low crosswind limitations. Typically the law of primacy cuts in and the same pilots can sometimes carry these faulty techniques throughout their flying career.

[JammedStab]

It looks like the main reason for the tailstrike was an excessive rotation rate at 5 degrees per second. Some aircraft are more vulnerable to tailstikes than others. I flew the 737-200 which was unlikely to ever have a tailstrike and was originally approved for a 6 degree rotation. But the -800 is an extremely long aircraft. Stick to 3 degrees per second and if you have to err, then err on the side of a slower rotation in aircraft like that.

Boeing does make mention of the effects of spoiler deflections but I have flown three Boeing jet types and a fair amount of aileron is necessary to keep the wings level in a significant crosswind. If I remember correctly, one of the types had spoilers picking up at a mere 2.5 degrees of aileron input. We rotated in strong crosswinds with plenty of aileron with no problem.

Rotate at the normal rate and as Boeing states, if it is a gusting crosswind, add a few knots to the rotation speed. It wont hurt.

For the Australian incident, the rotation was started 5 knots early which exacerbated the problem caused by the gusty conditions.