Speed Management

[zachlog 18]

I am assuming that cruise speed must be managed manually, i.e., this aircraft has no autothrottle capabilities, correct ? Other than setting the speed bugs, does the IAS switch (between the CRS and HDG switches) have any other role ? I guess what I am askling is does this switch make a direct contribution in managing the speed of the aircraft (other than trigerring the v1/vr/v2 announcements) ?Thanks,Zach

[michal 44]

I am assuming that cruise speed must be managed manually, i.e., this aircraft has no autothrottle capabilities, correct ?

Correct.

does the IAS switch (between the CRS and HDG switches) have any other role ?

Yes it does. You could use it for example during descents to maintain selected speed (pitch 'hunts' for speed rather than say VS). You could also use it during climbs. It can't be used in cruise however.

[CapP 0]

I myself use IAS during climb to have the maximum climb rate at the ideal climb speed (170 knots) and us v/s during descent between 1000 and 1500 ft/min. I keep the speed as high as possible with the throttle, normally around 230 knots (or is this a little fast?).

[michal 44]

normally around 230 knots (or is this a little fast?).

You are not breaking any rules, unless you violate some internal company policy .. :( One has to remember that when you climb you gain potential energy but you pay the price in terms of fuel burn ... theoretically you can get most of this energy back when you descend .. (unfortunately in driving it is rarely the case but in aviation you can get close to it). If you descend with speed close to what your climb speed was - you are flying optimally from the energy (fuel burn) point of view. If you descend much faster you will pay the price in fuel burn. But in FSX fuel cost is fortunately :( .. zero

[zachlog 18]

I myself use IAS during climb to have the maximum climb rate at the ideal climb speed (170 knots) and us v/s during descent between 1000 and 1500 ft/min. I keep the speed as high as possible with the throttle, normally around 230 knots (or is this a little fast?).

Michael and Pieter,Thank you for your responses but here is what puzzles me.I understand using IAS mode during climbs/descents and have tried it several timea but I modulate the IAS that displays in the EADI using the thumbwheel that is on the center console. Where does the IAS switch come into play ? Or are you saying that either the IAS switch or the thumbwheel can be used for changing the IAS setting ?Thanks again,Zach

[michal 44]

I guess we have a slight miscommunication here. What you refer to as 'switch' is really a knob - this one is used to set speed bugs only.Pitch wheel is used to set the currently selected IAS (if the IAS button is depressed = IAS HOLD selected). And this value shows up at the topof the speed tape. The best way to learn is to simply experiment with it, it is quite intuitive.

[rsrandazzo 6,353]

Gents-Dan is giving some good advice here.From a practical real-world perspective- here is how I used the pitch modes on the A/P...CLIMB: Trim to 170KIAS then select IAS mode on the F/D. This will give you optimal climb performance. (Note: When I first joined the fleet, we climbed at 160 KIAS, which gave us pretty good climb performance even with the engine Anti-Ice on. The FAA issued some directives on icing for turboprop aircraft- and it caused our company to bump the climb speed up by 10 knots. This tiny little change had a pretty noticeable impact on our climb performance if we had the engine heaters on...)DESCENT: Generally speaking I liked to come down in IAS mode. When issued a descent, I'd set the altitude then punch the IAS mode button on the A/P, and very slowly roll the speed forward using the thumb wheel on the autopilot control head. By slowly increasing the desired IAS, the airplane would very gently enter a descent and very gently accelerate. I'd keep rolling that thumb wheel until I had 230-240 knots depending upon the ride and the airplane. Some of the airplanes in our fleet would get really pitch-twitchy over 230knots KIAS. Others were rock solid. Heck- I had one hit the forward trim limit one day and unceremoniously dump the airplane back in my lap while the A/P threw a tantrum for the stupid pilot allowing it to run out of forward trim. (I think it was a CG issue- but it was pretty common in that one airplane to see it hit the forward trim limit!)

[Zachiii 0]

Thanks Robert.Your info is super. I am slowly learning to correctly fly this sophisticated bird.Zach