777-300ER C of G default...

[Marooned]

Hi Guys,

Frustrated with no feedback through internal channels both from Boeing and the company on any matters technical least of all this one, I wondered if anyone else has some thoughts or feedback on this issue:

When our company first received the 777-300ER we began experiencing wing flutter, a low frequency vibration eminating from the newly designed raked wing tips. We flew for several months with this until a Boeing directive instructed us to modify the default C of G to 7.5% which operationally reduced our max crz altitude by between 1000' - 2000'. This effectively mitigated what can only be described as a 'design fault'?

However, this solution has not only lowered our maximum crz altitude and given us a sometimes lower than optimum crz altitude, it has also modified our minimum and maximum displayed airspeeds.

My concern is that these new more 'conservative' speeds are still the 'incorrect speeds' when related to the actual C of G which invariably is between 25 - 32%. In severe tubulence the autopilot and 'us' the pilots will react to these artificial indicated speeds rather than those predicated by the actual C of G, which can increase the 'coffin corner' buffer by up to 15kts depending on the actual C of G and gross weight.

I have had no official feedback as I say but I like many others would prefer to see the actual speeds inflight and wondered why we should not enter the actual C of G once level.

Operationally I am aware that some are entering an interpolated C of G from the loadsheet in order to see the correct speeds but also that others are doing so to allow further climb for example to avoid weather...both techniques currently non-SOP.

Any thoughts? Does it matter? Still awake? Like to know.

[Thylakoid]

If you work for EK, there is a bulletin, EKIB-21 that describes this problem.
I felt the flutter many times before when flying above .084 M at high flight levels.
Apparently, as far as the default input of 7.5 in the cruise CG is concerned, that is a temp fix from Boeing. Flt Ops doesn't recommend changing the value since it doesn't affect fuel or aircraft performance.

[Marooned]

Thx Tylakoid.

I have read the bulletin and understand the problem. My concern is the fact that without any further guidance the effect of the 7.5% default is to present us with false airspeed information, conservative it may be, but it is inaccurate.

My contention with the info given from flt oops is that despite their assurances it does restrict our climb capability, which over the Bay of Bengal will lead to some bumpier rides than necessary and prolonged wx avoidances, and in some situations does give us to a lower than optimum crz lvl both of which does affect fuel burn.

In the extreme the autopilot will react to the false airspeed info. In effect are we not fixing one problem with the possibility of creating another?

I feel we need more info, hence the discussion here.

[Thylakoid]

I understand your concerns. I believe, though, that even Flt Ops or the Tech guys are pretty much in the dark about this. Sometimes, Boeing is not that helpful, either. It looks like they screwed up on the design, somehow. Aerodynamically speaking, that flutter shouldn't be there.