Basic question regarding Maneuvering Speed

[Guest]

Gentlemen,I was hoping someone could explain the presumed limitations to which the aircraft is subject to below Maneuvering Speed. I have assumed that is means turn limitations at certain speeds and flap configurations. But I do not know technically what they are; say no bank degree beyond 25% at flaps 15 - that sort of thing. Also, in my flying experience (as a passenger) it would seem that aircraft at times make quite sharp banks on final approach (KLGA) at reduced speeds and/or flap configurations. So what are the actual Maneuvering limitations?Any insight is appreciated.WS

[eurowing]

WS, i am not sure about bank angles and flap settings in a 767, but in general you must understand that the maneuvering speed is a determined MAXIMUM speed and not minimum. so there

[Guest]

Denis,Thanks, clearly I had the concept all wrong. So the correct question on my part would be what limitations are OVER this speed. But your response puts me on the right track.Regards,WS (KEWR)

[Guest Ian_Riddell]

"but in general you must understand that the maneuvering speed is a determined MAXIMUM speed and not minimum. so there

[Guest Ian_Riddell]

Found this shot on the internet (and modified it slightly for clarity)....http://members.ozemail.com.au/~b744er/ManoeuvreMargins.gif(A picture is worth a thousand words).Cheers.Ian.

[Guest HPSOV]

The speeds you are refering to are the minimum manoeuvre speeds (+20, +40, +60 and +80) for the various flap settings.All the speeds ensure the same thing, that the aircraft has a 1.3g manoeuvre margin before the onset of stall buffet.This equates to a 40 degree angle of bank, which is the maximum of 25 degrees, plus a 15 degree margin for overshoot.

[Guest]

Ian,Thanks for the detailed response! I was not as far off the mark as first thought.Regards, WS

[Guest Iz]

The official meaning of Maneuvering Speed (Va) is actually a maximum speed, as said above.For all aircraft, this is a speed where the aircraft must stall before structural damage occurs. This is why in very tubulent air, you have to stay at or below Va at all times. This ensures a 1.3g margin at full bank angle (but this is really up to the certification body, sometimes it's 1.2 or 1.25) before structural damage. It ensures adequate g-margin for level flight, up to the maximum positive g-factor certified plus that 0.3g margin (1.3 minus the 1g you already have in normal life, even sitting behind your computer screen right now). Go faster than that and the airframe may incur structural damage at certain g-loads, occuring very easily in turbulence. Now if you're at your maneuvering speed and you encounter a +4g downdraft, your wings will stall instead of bend or break. So when that downdraft is over you can recover instead of plummet to the ground with a damaged aircraft.Iz

[Guest HepburnUGA]

Sorry for the somewhat off topic post, but have you guys seen this? It looks like this guy has 35+ degrees of bank at surely very close to Vref, gear down, flaps 30. I can't make out the airspeed but on the F/O altimeter you can kind of make out the speed bug which I assume is at Vref + 5 or something close to it. Just curious to know the limitations on bank angle at very slow speed. I realize this is a 737 but the situation applies equally well to a 767. Wouldn't he be getting close to getting the stick shaker? They both look very calm :) Jeffhttp://airliners.net/open.file?id=297683&W...atic=yes&size=L--What a ridiculous URL

[Guest Iz]

You know there's actually a line above the picture that says:"The URL to this picture is:".. :)Anyway, the approach in Funchal is one of the more dangerous approaches in the world and it's quite a spectacular photo. Still, there's no special reason why a high bank angle would always cause a stick shaker. You can do 60 degree turns in the aircraft in level flight with power on, no problem, technically. From an operational point of view, it's not done of course.Iz

[Guest MB327]

We did that approach in our PIC on VATSIM flight at the end of last August. Apart from the real world view, that is a lot like what it looked like on the HSI and the turn was at least that tight. Search for "PIC on VATSIM screenshots" to see some of the great screen shots of the day, including one nameless 767 that went into the side of the mountain. On another note, I did the Expressway Visual to 31 at LGA with ACA856 and AAL1220 the other night, that is one hell of an approach at night with a crazy left turn in a 767 I can tell ya. Yes, we all made it but Rob mentioned needing to take a short break to change underware afterward.

[Guest Ian_Riddell]

Deleted (due jibberish posted) :-)

[de Lattre WGA]

hello,Attached you will find the manouvering diagramm speed for all JAR25 bird.Basicaly, the manouvering speed has a simple formula:Va=square root of 2.5 x Vs (stall speed)Vs is very important cause it will not be the same regarding the weight and flap setting as well as the altitude. In a previous message of this thread, you have a very nice picture of an EADI of a 767 at FL390, but it is not the Va. It is the range of speed usable at the present time. the upper red briks are showing the never exeed speed, and also the High speed stall point, and the lower red briks the stall speed. In between, you have to calculate the VA. Some good flight engineer, will do this for you.For any liner, you have to keep in mind that the Va is the calculated speed at which the pilot can use the max commands deflection with out damaging the aircraft. As you will see on the diagramm, the max number of G allowable before permanant deformation is 2.5, and the max before breaking the bird is 3.75.Upper i said that the stall speed was important, it is because this speed will vary regarding to weight, altitude and flap setting. For all Jar 25 bird, the max G allowable with flaps is 2.Thus, you will have to remain in the grey aera if you want to land safely and not being fired for permanant deformation.I can go deeper in this explanation for you if you want, but it is going to take a lot of time, and may be difficult to understand if you are not familiar with aerodynamics (advanced), and may not be helpfull o the other simmers.Any way, if you have any questions, just ask.Very best regards.Cpt Cyrille de Lattre

[Guest Ian_Riddell]

>For all aircraft, this is a speed where the aircraft must >stall before structural damage occurs. This is why in very >tubulent air, you have to stay at or below Va at all times.I'm still a little confused, Iz....Is Va the point at which you stall/experience buffet... or a lower safe speed (with the 1.3 factor)? Or are the two the same at high bank angles?For example, in the pic below of the 747-400 Primary Flight Display: Would you say that "Va" was at the bottom of the Max/Upper Manoeuvre Margin (yellow band) at the top half of the airspeed display, or elsewhere? http://members.ozemail.com.au/~b744er/AirspeedTape.jpgBecause the upper yellow manoeuvre margin band dangles from the upper red band, I thought that Va might be related to Vmo (i.e. the lowest red brick in the upper red band). However, from your description, I get the impression that the two might not be related (?).Thanks.Cheers.Ian.

[de Lattre WGA]

To me it looklike this isthe description of the Vb speed.Vb speed is the is the calculated speed range for max vertical gust intensity.Vb is the stall speed reached where an instant vertical gust is equal to:FL200 = +/-66ft/secFL500 = +/- 38ft/secIn order to be protected, you have to remain within the yellow range of those speed.If your speed is too high, regarding to the speed range and the yellow margins, you may experience in case of a instant vertical gust a high speed stall, for the upper part of it, and for the lower part of it a low speed stall with activation of the stick shaker and possibly the pusher.If you have selected a flap setting, this speed will be called Vf.Hope this helpCpt Cyrille de Lattre