Flying the 787

Could someone explain to me what they mean when they say the following:

"The aircraft is speed stable. So you the pilot have to trim nose up or nose down pitch in the air with speed change."

I don't get what they are saying.

As far as I understand, it means that unlike the Airbus, where autotrim means that the aircraft will trim for you in Normal law to hold a certain attitude, in the 787, you have to trim the aircraft yourself when hand flying.

Couldn't figure that one out either... Otherwise deffo looking wd to paxing on this thing, cabin alt 5-6k should make a, say, LHR-LAX a lot more enjoyable than the current 8.5k

Could someone explain to me what they mean when they say the following: "The aircraft is speed stable. So you the pilot have to trim nose up or nose down pitch in the air with speed change." I don't get what they are saying.

My interpretation of that sentence is that aerodynamically the aircraft is not statically stable in pitch, but that computer generated active control is utilized to make it appear that way to the pilot. Playing games in design with what we consider to be normal aerodynamic static pitch stability reduces drag.

Boeing is reputed to have a preference for making the aircraft more traditional (than Airbus) in its interface to the pilot, so it makes sense to me that instead of eliminating out of trim control forces, they would instead choose to make it feel like a 'normal' statically stable aircraft.

All of the above is only my guess on how to interpret the quoted sentence.

I would tend to agree.

Boeing are certainly trying to capitalise on high profile cases of alleged "muppet flying" like AF447 and the various issues which arise from the Airbus zero-feel control.

With silly stuff like stall warnings that are inhibited below 60kt, I'd think they are enjoying themselves almost as much as the editor of the Private Eye which must be inundated with material nowadays

Just my opinion of course

Thanks guys.

So what they are saying is not that it's speed stable (because if the auto throttle is off, and you pitch up speed will decay, and increase if you pitch down) but rather that it's pitch stable.

So if you change pitch angle, it will, like any normal aircraft, attempt to return to the original trimmed pitch and regain the original speed.

"Speed stable" seems like a terribe way of putting it!

It's possibly not quite the same thing.

A conventional plane will be speed stable only in a given configuration of loading, flaps, etc. Only in that configuration will a change in thrust not significantly affect the airspeed.

What Boeing may have done is a speed stability across configurations so the plane might fly the same way across the full range of loadings etc. With fly by wire, anything is possible, and consistent handling would make it easier to hand-fly.

But we are all guessing...