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Black_Dawn
6th Mar 2002, 18:29
Sometimes i hear controversial opinions about rotation technique when reaching Vr speed.. .My personal way is to rotate to the target attitude (18~20 degrees) in a continuos movement (it takes about 5 seconds to reach the attitude).. .I've seen other guys, during rotation, pausing at ~10 degrees attitude, for about 1 to 2 seconds, just to build some speed, then going to the target attitude.. .I'd like reading your opinions about your way to rotate, also taking into consideration a possible windshear encounter or engine failure during the rotation.. .. .Thanks. .B_D

Airbrakes6
6th Mar 2002, 19:20
On big planes, tailstrikes can ruin your day. As long as I have excess runway and obstecles aren't a big factor. I'm more inclined to rotate the aircraft to 9-10 degrees and let it fly away from the ground in this attitude before I rotate it to the full 18-20 degrees.

exeng
6th Mar 2002, 19:40
I was always taught 2.5 to 3 degs/sec resisting the tendency to reduce that rate (due to horizontal stabiliser in ground effect) which occurs at approximately 10 degs on the 737. In other words, pull through that ground effect.. .. .Always worked for me. So far!!

Track
6th Mar 2002, 19:55
The 737-800 is very critical with rotation, you have about 22 inches between tail and tarmac during liftoff. . .I use the technique airbrakes describes, let it fly..... .I was also told that the resistance you feel at about 10-12 degrees pitch is aerodynamically built in (more than just the ground effect) so as to reduce the risk of tailstrikes. . .-------------------------. .Track

scanscanscan
7th Mar 2002, 00:43
Just a point....According to the questioners profile he is flying a MD not a B737. Possibly he is seeking advice for his current machine, which is fine if they are all similar. Are they? . .We must be careful not give him any duff gen which could get him in trouble on his machine.

exeng
7th Mar 2002, 01:06
Quite right Scan+3,. .. .That is why I specified the 737-2/3/4/5. (Don't know about 7 & 8) The scarebus I now drive is different again. I would presume that any MD type would not suffer from the 'ground effect' I previously mentioned. . .. .By the way I'm not claiming any expert knowledge here, I've just been applying what I've been taught many moons ago.. .. .One other point, I would think that performance is worked out on the assumption that the A/C is rotated smoothly at the correct rate through to the correct pitch attitude. . .. .Regards. .Exeng

HOMER SIMPSONS LOVECHILD
7th Mar 2002, 01:30
Can't be bothered looking up the exact wordage but certainly on the 757 Boeing prescribe a "continuous smooth rotation at 2.5 degrees per second to the target pitch attitude"(or words to that effect)They most certainly do not mention anything about "pausing" at 10 degrees-which is roughly the point of MINIMUM tail clearance.I find many people do that unintentionally due to the afformentioned characteristics.As a wise old American said on pprune some time ago "Son,if Boeing don't recomend it-don't go stickin' your dick in there"

Pegasus77
7th Mar 2002, 05:27
Airplanes are certified with a 2.5-3deg/sec rotation technique at Vr.. .. .The effect at 10 degrees happens in most airliners, even in my FBW-scarebus. It is purely aerodynamical, and not built in to prevent a tailstrike.. . . .If your take off calculations are right, and you rotate at Vr with the given 3 degrees per second, your tail won't strike the ground. . .. .Even worse, if you apply your house-built rotation-technique, your performance calculations wouldn't be right, because the V2, the 35ft-screenheight point and your 2nd segment climb would be somewhere different than calculated.

Black_Dawn
7th Mar 2002, 13:17
Pegasus,HSL,exeng. .. .that's what i wanted to get at: performance issues. Never heard stabilizer ground effect issues on the MD. .I know that with runway ahead and no obstacles, pausing a moment around 10 degrees of pitch attitude isn't going to ruin the take-off; but what about if at 10 degrees your engine decide to quit? or you encounter a windshear? I think the aircraft will sink much more than if it was at a steeper attitude.. .What I'm saying is that if you reach your target attitude ,and "trouble" starts, you are going to experiencing just a flattening of your take-off gradient, but if you are "pausing" at ~10 degrees pitch attitude, and "trouble" starts, you are in for a bad sinking, even if (pausing at ~10 degrees) your are building speed to trade to regain the positive gradient.. .So,what do you think?. .. .Thanks. .B_D

jumbo Mouse
7th Mar 2002, 13:30
Black Dawn. .. .I think it is rather a personal call. I must however say, on all large wide-body jets the normal AOM will state a continuous 3 degrees per second to the required T/O pitch angle for all engines operating. My personal preference is to rotate to one engine out pitch attitude, say 13 to 15 degrees, take a quick glance at the speed to see it is above V2 and accelerating at a normal rate, then continue onto normal all engine pitch attitude. At least I am then sure if I do have an engine failure all I have to do is go back to the one engine-out attitude and I will be well within the required performance criteria!. .. .Regards. .Jumbo Mouse

ft
7th Mar 2002, 15:54
I don't pilot airliners for a living, but I'd like to get a word in here anyway.. .. .As you'll have more drag at 10 degrees pitch than before rotation, why would you want to accelerate at 10 degrees pitch? If the airspeed is what is worrying you, you could accelerate faster if you just delayed your rotation.. .. .You all know the reasons for not delaying rotation I guess and I think the same applies here.. .. .Cheers,. . /ft

Airbrakes6
7th Mar 2002, 21:12
"but what about if at 10 degrees your engine decide to quit? or you encounter a windshear? I think the aircraft will sink much more than if it was at a steeper attitude.". .. .As for windshear, many manuals tell you to delay rotation and build up "smash". Some companies do this procedurally to improve revenue loads. My company calls this delayed rotation, "Improved Performance Takeoff. As for an engine quitting, you'll have so many more visual refrences available to you at 10 degrees. Look out the window and "step on" the runway centerline. I've flown military heavies where, accelerating in ground effect with an engine loss was standard procedure. In the equation of lift, V squared is the dominant figure, not AOA. At 20 degrees, you'll have a more dynamic situation and you're closer to the ground. . .. .Anyways my 10 degree technique presumes excess runway and no obstecles. I've always felt the plane will fly when it's damn well good and ready to. I'll only force it to fly if I'm running out of runway or have to clear an obstecle.

Captain104
7th Mar 2002, 22:39
Black_Dawn,. .your handling technique seems perfect to me. Rotation of 2.5-3.0/sec was SOP for 747 classic when I received training in Roswell 25 years ago. At 10 we used to stop just a moment(1-2 sec)as you describe and than continued rotation straight to required T/O attitude. The related point as tailstrike(there are others)has been covered by some posters. Kept this habit on heavy AB too.. .. .To stop the rotation at 10 and remain there til lift-off as proposed here(misunderstanding on my side?)is a procedure I wouldn't dare to mention. Performance requirements, engine failure case, windshear, obstacle clearance a.s.o. have to be kept in mind. <img border="0" title="" alt="[Wink]" src="wink.gif" /> . .Generally, stick to aunt Boing manuals to avoid being trapped in a place you can't enjoy as "dick"! <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

john_tullamarine
8th Mar 2002, 04:51
If I may offer some thoughts ... .. .(a) the manufacturer prescribes recommended rotation practice and one probably ought not to vary from this without a compelling reason .. much harder to explain the accident away. In general, the intention is to schedule Vr such that, . .. .(i) with a V1 failure and . .(ii) at the nominated pitch rate and. .(iii) using the nominated technique. .. .the aircraft will achieve somewhere in the vicinity of V2 at screen.. .. .(b) if one is concerned about windshear, surely it is better to delay rather than to interrupt rotation for reasons of predictable rotation distance and tail clearance. Others have highlighted this concern above.. .. .(c) many aircraft with a low tail will experience a very noticeable ground effect reduction in tail lift during the rotation. In such cases the rotation becomes a manipulative artform if it is to be performed smoothly. . .. .(d) the 737-800 has, I believe, an intentional stab trim mistrim schedule to increase the apparent control loads during rotation to reduce the risk of excessive pitch rate and tailstrike. Certainly I understand that one operator discovered that, by trimming a little more noseup, the rotation was much easier. When queried, Boeing suggested that this was not a very good idea.. .. .(e) the rotation is a skill like any other .. it is learnt and an appropriate level of skill achieved. .. .(f) if one is scheduling an overspeed or improved performance takeoff, then the story is the same as for a minV2 schedule - there is no "delay" in rotation, the rotation speed schedule is quite intentionally increased to achieve an improved OEI second segment climb gradient.. .. .My main concern in reading this post is in regard to SOPs .. don't we adopt SOPs precisely to strive for a repeatable, reliable outcome ? Do it yourself techniques and procedures may have a place in some areas of aviation .. but, in scheduled operation ?

4Greens
8th Mar 2002, 05:02
Have done recorder analysis of tail strikes on 767's. Every time it was a too fast rotate that did the damage - not the attitude. A bit of bank helped as well.

411A
8th Mar 2002, 06:57
As usual, JT is right on target. . .Have found that at MAX weights, a "slightly slower" rate of rotation is helpful (TriStar)...but have found that my F/O's don't always agree, but they still do it my way nonetheless...never insist, just suggest.

Prince of Dzun
8th Mar 2002, 16:17
To all:. .. .The makers of the aircraft you fly know best. Do what they suggest, stick to the SOPs and use the armrests because the armrests are the secret to good rotation.(Boeing and Lockheed suggest they should always be used). Why think too much, keep some space in your brain for something real.. .. .Prince of Dzun

Blip
8th Mar 2002, 17:33
I would have thought that an absolute text book rotation rate would only be critical when at length or obsticle limit weight and you have an engine failure right at V1. After all, that is what all the performance figures are based on.. .. .Once you reach V1, every moment after that spent operating without an engine failure is bringing you further and further away from the edge of the required performance envelope.. .. .So if you've made it all the way to Vr and you still have all engines operating, bonus! I think in that case you can afford to REDUCE your rate of rotation from say 3 deg/sec to maybe 1 degree per second passing through 9-12 degrees nose up.. .. .So it takes an extra 2 seconds to reach the target attitude (3 seconds to pass through 9-12 degrees nose up instead of 1 second)(6.8 seconds not 5.6 seconds to reach 17 degrees nose up). So what. The recommended rate of rotation is 2.5 to 3 degrees per second for the B733 so there is a difference of 1.2 seconds for a rotation to 17 degrees nose up right there.. .. .If a reduction in rate of rotation when the tail is just 2 feet off the runway greatly reduces the chance of a tail scrape, and it's not absolutely critical for performance reqirements for the reasons stated earlier, I think it's a good compromise.. .. .Anyway I doubt whether people are actually stopping the rotation at 10 degrees nose up. I think it's just a matter of greatly reducing it for 3 seconds or so.. .. .If however you are taking off at limited weights and the brown stuff hits the spinning bits, then yes, you might have a point. But even then I come back to the point that it's only a matter of an extra 2 seconds to reach the target attitude (in this case 13 to 15 degrees or so).. .. .Maybe that sounds unreasonable. Tell me if it does and why. I always like to share ideas and learn.. . <img border="0" title="" alt="[Smile]" src="smile.gif" />

Wino
8th Mar 2002, 18:38
If you don't always rotate at 3 degrees per second, how are you gonna do it when you absolutely need it?. .. .With the advent of reduced power takeoff every takeoff is the equivelent of a max weight performance limited takeoff so should you chuck an engine you will NEED that 35 feet.. .. .Delaying rotation is an enourmous hit.. .. .Just do it right, not half assed. .. .Cheers. .Wino

lord melchett
8th Mar 2002, 19:22
As far as technique is concerned, how do you experienced guys actually rotate to achieve the 2.5/3 deg/sec? Is it the old "one thousand, two thousand" etc?

Flight Safety
9th Mar 2002, 09:26
To JT, Wino, 411A and others, this is a very interesting topic. I'm concerned as to why some want to REDUCE the rotation rate.. .. .Is it because if you somehow miscalculate MinVr to too low a value, then do the normal rotation rate of 2.5/3 degrees per second to the correct pitch attitude, you will then get a tail scrape? It seems to me that this procedure requires that your MinVr calculation be correct, otherwise a pitch attitude of 15-17 degrees WOULD result in a tail scrape if the aircraft stays on the runway.. .. .Here's an example to illustrate my question.... .. .NTSB Identification: DEN90LA046 . The docket is stored on NTSB microfiche number 40608.. .. .Scheduled 14 CFRPart 121 operation of Air Carrier UNITED AIRLINES. .Accident occurred Tuesday, January 16, 1990 at NEW YORK, NY. .Aircraft:BOEING 757-222, registration: N505UA. .Injuries: 176 Uninjured.. .. .WHILE PREPARING FOR FLT IN A BOEING 757, THE 1ST OFFICER (FO) INADVERTENTLY COMPUTED THE TAKEOFF DATA BY USING THE BOEING 767 DATA. V1, VR & V2 SPEEDS WERE CALCULATED TO BE 115, 118 & 129 KTS. THE CORRECT SPEEDS SHOULD HAVE BEEN 145, 148 & 152 KTS. THE CAPT DID NOT CONFIRM THE V-SPEED COMPUTATION; BOTH PLTS SET THEIR AIRSPEED BUGS AT THE IMPROPER SPEEDS. DURING LIFT-OFF, THE ACFT WAS OVERROTATED & THE LOWER AFT FUSELAGE CONTACTED THE RWY. THE CREW NOTED A 'JOLT,' BUT ELECTED TO CONTINUE TO THEIR DESTN AFTER DISCUSSING THE SITUATION WITH MAINTENANCE PSNL. AFTER LANDING, DAMAGE WAS NOTED TO THE LOWER AFT SKIN, AFT PRESSURE BULKHEAD & ASSOCIATED STRUCTURE. . .. .The National Transportation Safety Board determines the probable cause(s) of this accident as follows. . .. .OVERROTATION OF THE AIRCRAFT DURING TAKEOFF. FACTORS RELATED TO THE ACCIDENT WERE: THE FIRST OFFICER'S IMPROPER USE OF THE FLIGHT MANUAL, WHICH RESULTED IN HIS IMPROPER CALCULATIONS OF THE ROTATION SPEED, AND INADEQUATE SUPERVISION CONCERNING VERIFICATION OF THE TAKEOFF DATA BY THE CAPTAIN.. .. .(Edited to insert the NTSB example). . . . <small>[ 10 March 2002, 03:42: Message edited by: Flight Safety ]</small>

Prince of Dzun
9th Mar 2002, 11:35
411a:. .I flew the Lockheed 1011 for five years and I don't remember any different " feel" at heavy weights. Also the Lockheed training captains who were also Lockheed production test pilots never suggested anything about modifying the rotation rate under any conditions. Their attitude was do it the same each time and that was good enough for me. What is your reasoning for doing it differently ???. .. .Blip:. .You think too much. If you don't do it corectly all the time how in the name of heaven are you going to do it right when things are going wrong.. .Different type ratations on different days does not make sense to me. . .. .Lord Melchet:. .It's something someone else ( the expert) teaches you. First it feels right, second it looks right and third it is right. You don't need any fancy number counting. . .. .Prince of Dzun

411A
9th Mar 2002, 15:08
Prince of Dzun--. .Should an engine fail just at rotation on a max weight takeoff, the climb out at V2+10 is much easier than at V2, especially for very junior F/O's.

Prince of Dzun
9th Mar 2002, 16:03
411A:. .That's all very well but you seem to be forgetting that with a balanced field length you still must achieve the screen height. You and I know balanced field lengths are sometimes hazardous affairs and they are often followed by obsctacles which make the screen height marginal. Why not do it everytime the same way so that when the max effort day arrives it is just a little easier.. .. .Prince of Dzun. .. .P.S. I have a definite view on whether the call should be " rotate" or " vee ah" and I'd be pleased to hear your views on this prior to a discussion.

411A
9th Mar 2002, 21:47
Prince of Dzun--. .The correct terminology should be IMHO, "rotate".. .Many it would appear(especially in the UK) have a fixation about screen height. This is all well and good, however, in order to achieve controled flight, one needs to keep the blue side UP. The margin of error at V2+10 is MUCH greater than at V2.. .Reference the AA DC-10 accident at KORD a few years ago. In simulator reinactments, those pilots (very few actually) who put the nose down to achieve flying speed did not roll over on their backs. If you cannot maintain the blue side up, screen height has little significance.. .These are my views anyway, and they have served me well for over 35 years.

Zico
10th Mar 2002, 14:33
Excuse me my ignorance, but the poor fellows at KORD were (I believe) convinced that they had enough speed. Hence they saw no need to lower the nose until it was too late.

Prince of Dzun
10th Mar 2002, 15:42
411A:. .I have to concede your argument is sound, however if you pin the attitude exactly (good rotation) and hold it steady (neutral aileron and correct rudder pressure) the aircraft will climb all day with an engine out and the speed right on V2. Why should she roll over? Well, she will roll over due to fiddling around and if you want to build in some protection for that then you certainly have a point. Nevertheless, I always felt I was paid to enforce the SOPs and that's exactly what I did. I never had to do it for real and I consider I was lucky considering I spent more than two years off the surface of the earth. Regards,. .. .Prince of Dzun. .. .P.S. Pleased to see you go for " rotate" because I go for "Vee ah". I'll give you my reasons for this tomorrow.

Wino
10th Mar 2002, 20:51
411s answer is [tut tut!].. .. .The Ord DC10 crashed because all the Leading Edge devices retracted on the right side of the aircraft after the engine pylon seperated from the wing damaging the hydraulics. At the time there were no downlocks on the Slats, they were simply held down by hydraulic pressure. During the grounding of the DC10 , that was one of manythings that had to be fixed before the DC10 was allowed to fly again.. .. .Targeting v2+10 is normal procedure on rotation now. You go strait to it with now hesitation. If you get airborne and then lose an engine you hold what you got. If you chuck an engine at V1 that same rotation takes you right to v2. Its a beautiful thing. Samething everytime.... .. .Cheers. .Wino. . . . <small>[ 11 March 2002, 04:25: Message edited by: Checkboard ]</small>

Prince of Dzun
11th Mar 2002, 10:17
411A:. .When the word "rotate" is spoken or shouted it comes across the flight deck as a command to do something and do it now. This in turn tends to raise the temperature a little and the pilot flying reacts accordingly by (in extreme cases) hauling the aircraft into the air rather than flying it into the air with a smooth steady input. The "increase in temperature" can cause a tail strike especially on short runways when the shouter is sometimes phased by the end of the runway rushing towards him. On the other hand, "vee ah" tends to be spoken quietly and comes across in an advisory capacity. The pilot flying then reacts more sedately with a correspondingly smooth more controlled rotation. The company I flew for operated Convair 880, B707, L1011 and B747. Armrests and "vee ah" was what they insisted on and I did this for 20 years on the four different types. To my knowledge there was never a single tail strike over the entire period and I often thought that perhaps "vee ah" contributed much to this excellent record. Over to you.. .Regards,. .. .Prince of Dzun

Prince of Dzun
12th Mar 2002, 16:36
Wino:. .I do not agree with what you say about attitude and V2. You cannot expect to hold V2 with an engine failure at V1 if you don't reduce the normal pitch attitude by some small amount. My memory for the B747 classic puts this at 2 degrees less for 3 engines. Company procedures required the take off data card to be displayed prominently for both pilots to see and the top lines on the card (in big printed letters) said:. .. . 4 engines 15 degrees. . 3 engines 13 degrees. .. .This took care of the max take off weight engine failure at V1 as 13 degress always without fail gave exactly V2. Of course any weight less than max gave a higher speed. The point is that by holding the selected attitude steady the climb out profile was always assured. Easy: no thinking required. It was not for me to question this. My job was to do it. In conclusion, I must say I never flew a big twin so perhaps they are different. . .There is something magical about the perfect rotation. All that weight slotted just where you want it and with so little effort. Equal to a good landing because it's a small personal achievement. No one knows about it except yourself.. .. .Prince of Dzun

411A
21st Mar 2002, 11:21
Well Prince of Dzun, your point about Vee ah..is a good one and if it worked for you all those years, then who am I to critisise. I have worked for five different companies (sixth soon) operating the TriStar and they all did it differently. Strangly, none used the Lockheed recommended checklists or procedures exactly...yet Lockheed spent a LOT of money developing these procedures. In our new venture, I am in a position to insist how it will be done..and it will be Lockheed all the way. Lockheed will send us a tech rep as well who will ride around with our crews (many of which have never flown the aeroplane) to try to standardise procedures. There will NOT be any "..well we did it this way at BA.." with our guys.

john_tullamarine
21st Mar 2002, 13:24
411A,. .. .I could always be talked into coming along and helping out .......

Mud Skipper
21st Mar 2002, 23:27
Perhaps it's embarrasing to admit I think I still move my lips as I rotate. One thousand, two thousand, etc. I've found a continuous rotation works just fine, yes the aircraft may lag around 10 deg. Final pitch settling down with V2+20, we always use ICAO B for departure unless ICAO A is stipulated.

Chesty Morgan
22nd Mar 2002, 18:48
Just to let you all know, I was going through the motions of a slower rate of rotation, as the aeroplane flew itself off at about 10-12 pitch we had a fairly large loss of airspeed (gust/WS) and this resulted in us being airborne for a slightly shorter time than intended!! The resultant touchdown was sufficiently hard enough to stop me doing it again.