Overspeed and the real world

[Guest ssurjap]

I know FSX doesn't do a good job with winds, but I'm just wondering the following: For all you real-world pilots out there (especially those operating passenger jets), do you ever run into situations, in the real world, where you have Auto-throttle engaged and autopilot on and your aircraft goes into Overspeed?I'm asking this because every time I fly either the default 737-800 (and a Posky 757) in the Mt. Rainier area, my aircraft will always go into Overspeed because of the wind change.I set the auto-throttle on and autopilot on, with my airspeed at .02 or .03 (sometimes even more) below the cruise mach and it always goes into overspeed.Thanks.

[mabe54 17]

Stephen:It looks like you are being played by the wind. Let's say your airplane is cruising at 0.84 with headwind and all of the sudden the wind changes to tailwind your speed will go over-speed until the the auto-throttle catches up but the plane has still to decrease its momentum. I normally set it first to -0.02 match below max of 0.84 (depending on the airplane of course sometimes max is just 0.80 or less). It is really a guessing game. But if the day looks clear, pedal to the metal if not reduce speed especially in turbulence. It gets more complicated for pilots to get the best max speed in real life.I hope it helps,Cheers,MAB

[Guest ssurjap]

Thanks, I appreciate it.

[vololiberista 205]

Certainly it's a weather thing! If you are encountering turbulence then slow down to the "rough air speed" Which should be about half way between Vb and the maximum strength speed for compliance with 66ft per sec. gust ratio. If you are in 'apparently' good weather then leave a margin for clear air turbulence. (see BOAC Tokyo 1966). don't forget to use mach numbers above FL240!!!Vololiberista

[UDflyer 0]

I'll preface by saying I don't fly jets yet, but in my years of flying single and multi-engine piston airplanes I've never seen anything like what FS does in turbulence. I've never seen such abrupt airspeed changes in real life as I've gotten in FS, although I will say that I've never flown in windshear or a microburst before, either. :( However like everyone said, you don't fly at VMO or MMO during turbulence anyway, so that shouldn't be a problem. I did experience something rather interesting not too long ago when I was flying from my hometown down to Atlanta on ASA. I was in row 4 or 5 and I could hear them disconnect the autopilot, which is normal, but I could tell we were high and fast. As soon as I was thinking that they extended another notch of flaps and I could hear the flap overspeed warning go off for about 5-7 seconds. I wonder if they wrote that one up or just let it go. :(

[vololiberista 205]

A footnote regarding turbulence. The worst experience I have ever had was in 1974 returning from Iran in a VC10 over Istanbul. We hit clear air turbulence which deflected the wingtips by I would say at least 8-10 feet the lift letting go and then flexing by the same amount like a ruler! We dropped like a brick for at least 500 feet before recovery. This happened twice. The pilot obtained clearance to FL450 and we thereafter had a comfortable journey home.The captain came back through the cabin to see that everyone was ok. I told him about the wings and he was quite convinced that had we been a 707 they would have come off. He obviously had in mind the tragedy in 1966. The VC10 is I believe the only passenger jet transport to have an aerobatic licence!!Vololiberista

[mabe54 17]

Those are the times when EVERYBODY, regardless of believe or not, ring GOD's phone number.Cheers,MABAMEN!!!

[FlightLevel180 0]

Those are the times when EVERYBODY, regardless of believe or not, ring GOD's phone number.Cheers,MABAMEN!!!

Amen!

[John_Cillis 2,406]

Stephen:It looks like you are being played by the wind. Let's say your airplane is cruising at 0.84 with headwind and all of the sudden the wind changes to tailwind your speed will go over-speed until the the auto-throttle catches up but the plane has still to decrease its momentum........MAB

The opposite is true. If a headwind changes to a tailwind, while the ground speed may initially increase, the airspeed will drop. If the opposite happens, overspeed is possible. Remember, an aircraft's airspeed whether measured in knots or by mach# is relative to the air around it, not the speed over the ground. In the small microlights I fly I have to be careful when approaching in a gusty headwind since my approach speed may be 40 kts or less and the stall of the smallest of the aircraft I fly is only 20-22 kts. If the headwind suddenly drops, I can find myself very close to stall. That's why we generally fly only in the early mornings or late afternoon when winds are calm. But I have also a friend get caught by winds when flying with him in his 172, where a sudden drop of the headwind during the flare caused a hard landing with the stall horn blaring ten feet above the ground...-John

[vololiberista 205]

The finest a/c in the world (the one to my left!!) the only a/c to ever have an aerobatic licence is interesting in cross winds. Cross wind landings are, one could say its Achilles Heel. Not that it can't handle them. The wings are so clean that when landing one has to be positive and anticipate what the VC10 wants to do. After a while it's second nature though.Vololiberista

[Gavin 99]

Those are the times when EVERYBODY, regardless of believe or not, ring GOD's phone number.Cheers,MABAMEN!!!

Whilst some others may involuntarily defecate, something they wouldn't do in normal life. A shocking and terrifying situation can lead people to irrational thoughts or actions.

[Vagabondo 23]

I know FSX doesn't do a good job with winds, but I'm just wondering the following: For all you real-world pilots out there (especially those operating passenger jets), do you ever run into situations, in the real world, where you have Auto-throttle engaged and autopilot on and your aircraft goes into Overspeed?I'm asking this because every time I fly either the default 737-800 (and a Posky 757) in the Mt. Rainier area, my aircraft will always go into Overspeed because of the wind change.I set the auto-throttle on and autopilot on, with my airspeed at .02 or .03 (sometimes even more) below the cruise mach and it always goes into overspeed.Thanks.

As a 737 pilot I can say yes and no. Overspeed in the sense of MMO/VMO is very unlikely at altitude due to windshere. Wind gusts are a product of the boundary layer effect near the ground. Significant windshere at altitude could be theoretically possible if turning from a tailwind into a very strong headwind but I have never seen it. Rather like the mythical downwind turn.However, overspeed is possible in the 737 in VNAV PATH mode if you get significantly above the descent profile. In VNAV PATH the aircraft will just pitch down to recapture the profile, a distracted crew could get the clacker!

[Guest belga1]

Hello,

Overspeed and the real world

The results of the investigations about the AF447 (if any significants found) will maybe give som light on the overspeed problems.Regards.Gus.

[vololiberista 205]

Hello,The results of the investigations about the AF447 (if any significants found) will maybe give som light on the overspeed problems.Regards.Gus.

You need to see the discussion on the thread dealing with that accident. "overspeed" or a problem with the pitot tubes is much more likely to be affect and not cause.Vololiberista