B777RR to GE Take-off differences

[applecrumble]

Does anyone know any reason why the B777-200RR895 feels much sticker when unsticking at VR compared to the B777-200GE or even the B777-300GE?

I can’t think of any particular reason why this would be the case but it seems to be.

apple

[FullWings]

I don’t know for sure but it could be a problem with the trim calculation. They have been like that since they were introduced - on my first go on an RR variant I thought there was a serious flight control issue when it came to rotate as the forces were so much higher than the GE versions.

For quite a while as SOP we added some back trim to the FMC value to bring it closer to the GE experience but Boeing got wind of that eventually and put the kibosh on it. I joke about having developed a specific set of exercises to do in the gym before a RR flight but it does catch people out who are new to type and haven’t experienced or been briefed about it yet.

I don’t think it’s anything to do with the engines themselves, just (IMO) the trim setting algorithm in the FMC is getting it a bit wrong but the aeroplane flies so no-one can be bothered to fix it. A bit like the blockpoint update which left the plane much worse at holding than before that hasn’t been improved since.

[MrBernoulli]

Originally Posted by applecrumble

Does anyone know any reason why the B777-200RR895 feels much sticker when unsticking at VR compared to the B777-200GE or even the B777-300GE?

Originally Posted by FullWings

They have been like that since they were introduced - on my first go on an RR variant I thought there was a serious flight control issue when it came to rotate as the forces were so much higher than the GE versions.

Having flown the 777-200 RR and GE engine variants (and also eventually the 777-300 GE) for around 17 years, I cannot say I ever noticed much of a difference in the elevator feel at rotation and lift-off. 🤷🏼‍♂️

I do recall the pitch trim setting calculation differing for the RR variant, a procedure which then later disappeared, but I didn't dwell on it. I just looked over the nose of the aircraft and did as was necessary with the elevator to get the required pitch rate, in order to then meet with the flight director pitch bar for the climb away from the ground.

Originally Posted by FullWings

A bit like the blockpoint update which left the plane much worse at holding than before that hasn’t been improved since.

Yes, the FMC holding pattern for the 777 was initially quite acceptable, but after one particular software update, it then became sloppy and untidy. I assumed that might have something to do with reducing the number of lines of code, or characters, in the software, due to the ridiculously small amounts of memory in the FMC that were now having to be filled with steadily more complex and stringent precision approach stuff? But that is merely my assumption.

[FullWings]

​​​​Having flown the 777-200 RR and GE engine variants (and also eventually the 777-300 GE) for around 17 years, I cannot say I ever noticed much of a difference in the elevator feel at rotation and lift-off. 🤷🏼‍♂️​​​

That is interesting. I find it pretty differentiated, including both the force required during the initial rotation and the position of the yoke to get the aircraft to pitch up. The GE variants seem to need much less elevator and almost leave the ground of their own accord once the rotation is under way, save for the little hiatus (common to all) as the stab/elevator goes into ground effect. I do fly other aircraft with what would be regarded as very low stick force per g, so maybe I’m being overly sensitive? Does seem to be a common impression amongst those I operate with, though.

[Jwscud]

I certainly had the same impression when I flew it. My impression was solely a difference in force required to initiate the rotation.

My sole uneducated guess was due to the N3 on the RR was higher gyroscopic inertia from the engines resisting the initial rate establishment. Hopefully tdracer or fdr will be alon to tell me if I’m talking rubbish or not!