The BIG gyroscopes…

[3WE]

…not the little ones in the panel.

Berntie implied that reduced-power takeoffs were done to reduce the gyroscopic forces on the engine fans when the plane rotates to its climb attitude.

I had always ass-umed it was driven more to reduce the infamous Turbine Output Temperature.

Question 1. Have you ever heard of gyroscopic-force concerns for the engines of any current airliner and that they are a reason for reduced power takeoffs.

Question 2. It SEEMS like Berntie also said that power was sometimes increased AFTER takeoff. I have never noticed any such thing for ANY reason, other than the power being increased AFTER an interim level off.

FAO: Gabriel

1. I know you can whip out some gyroscope mathematics. I wish you wouldn’t.

2. It is possible you may know something of this regarding aircraft engine and mount design.

3. If so, please initiate a reply in the aviation section, flyboy is protective of his forum.

Thanks.

[Gabriel]

Not going to answer the question 1. Just mention that a 20-blades, 1.5 Gabitos diameter fan spinning a C-152 redline RPM's must have... interesting... gyroscopic effects. And that GE and RR probably know it.

Also going to mention that it was me, not Brent, who said that many times the reduced take-off thrust is less than the climb thrust, leading to the thrust being increased when you reach the thrust reduction height. That's a fact. But I will of course let Flyboy answer question 2, whatever the question is.

[flyboy2548m]

Question 2. It SEEMS like Berntie also said that power was sometimes increased AFTER takeoff. I have never noticed any such thing for ANY reason, other than the power being increased AFTER an interim level off.

This was addressed in these pages previously, a good explanation was given, Gabito disagreed.

[flyboy2548m]

https://airdisaster.info/viewtopic.php? ... ust#p74072

[Gabriel]

I have to admit that your memory is hell better than mine. I had totally forgotten that I asked that question 7 years ago.
Not sure why you say that I disagreed.

[flyboy2548m]

Not sure why you say that I disagreed.

Even if you didn't, I'm sure you wanted to.

[3WE]

As to the main question, and upon further thought, I think Berntie is *among a small minority of pilots who “consider” power settings to limit gyroscopic forces during rotation.

We concur that those big ole, multiple fans have some gyroscopic effects, and I’m sure, that in the history of aviation, some metal has scraped other metal.

BUT

A nice, normal takeoff probably stresses things a lot less than a long list of stuff, including robust design limits for all sorts of aggressive ‘maneuvering’.

So Gabe’s buddies call for stout bearings, and that nasty lubricating oil.

/logic-based, ass-umptions.

*Flyboy may use different wording.