Hi I am familiar with the takeoff procedure but I wanted to find out why takeoff procedures say to rotate to 10 or 15 degrees when a tail strike can happen at 9.8 degrees? I was at the LGA airport recently and noticed all jets rotate maybe to about 7 degrees and wait to they are airborne before pulling the nose higher up. Is that why the FD commands 7 degrees in TO TO mode? I know the aircraft becomes airborne by the time you reach 15 degrees, but isn't it proper to rotate to about 7 degrees and wait until the aircraft leaves the ground before pulling to 15 or 20 degrees? Thank you. :-)

If the rotate is commenced at VR at 2 degrees per second Mr. Boeing reckons that a constant rotate to climb attitude will cause the aircraft to lift off at 7 or so degrees. If the rotate is halted the aicraft often busts through V2+15, coming close to or busting the limit for certification of V2+25. Tailstrikes are most common is crosswind or engine failure situations as the pilot flying instictively pulls back to get away from the ground, exceeding 2 degrees per second. Often the tail hits once the mains are airborne! Some of our aircraft print out a takeoff report that includes pitch rate, tail clearance, pitch and speed. I average about 3' clearance, the lowest I've seen is 1.5' (all for the -300 of course).

> but isn't >it proper to rotate to about 7 degrees and wait until the >aircraft leaves the ground before pulling to 15 or 20 >degrees? Thank you. :-) Yes. You are correct in your assessement. Documentation I have on the 767 states a rotation not to exceed 8 degrees as 9 degrees results in a tail strike.In general, once a positive rate of climb is established the pitch is increased as necessary to maintain V2+10. That pitch is maintained until reaching acceleration altitude (typically 1000 ft agl) whereby you reduce the pitch and begin the flap retraction schedule as the aircraft accelerates.-michael

mmcevilley,I have to say I believe anthonyj has the correct response. The risk of a tail strike is more related to the rate of rotation than the final target pitch attitude.For the -300 the Boeing recommended rotation rate is 2.0deg per second. They do not recommend hesitating at 8 deg or so. If you rotate at Vr at 2.0 deg per second you will not have a tail strike. The problem is either with an early rotation (not very likely) or more likely, too rapid a rotation rate.To meet the target airspeed window (and obstacle clearance and performance certification requirements) the pilot should rotate at Vr at 2.0 deg per second. As he stated, if you were to hesitate at about 8 deg n/u then most likely you would exceed the V2+15 to V2+25 target airspeed window unless you were very aggressive in the subsequent rotation rate.Kevin in CYOW.

>mmcevilley, >>I have to say I believe anthonyj has the correct response. >The risk of a tail strike is more related to the rate of >rotation than the final target pitch attitude. >Agreed - and I shall update my procedure as a result. ;-)-michael

However, if liftoff doesn't occur at 8

AAHHH, It's so nice to come across posts by knowledgeable people. I love technical discussions, as these are why most of the "serious" folks frequent these forums. Very interesting subject guys, keep it up.Tony P.

>AAHHH, > It's so nice to come across posts by knowledgeable >people. I love technical discussions, as these are why most >of the "serious" folks frequent these forums. Very >interesting subject guys, keep it up. >>Tony P. Tony,I'll take you up on that ... :-)With regards to the constant rotation rate of 2 degrees per second and the climb being initiated at ~7 degrees... is that typical for the entire takeoff envelope?The engineer in me believes that a lightly loaded aircraft upon reaching Vr will be accelerating at a faster rate than a heavily loaded aircraft when it reaches Vr. (In fact, at any single gross weight, the rate of acceleration will increase to some maximum, and then decrease until reaching a rate of 0 acceleration - provided the aircraft stays on the ground that long ;-) ). If the above is true then chance of "blowing" through V2+x is greater at lower takeoff weights than at higher weights, and, the chance of a tail strike is therefore greater at higher gross weight takeoffs.Any comments?Thanks.-michael

Not necessarily.When you are light, you can use thrust derates. On an eternally long runway (something like 4000 meters) you can enter a very high assumed temperature (provided you are nowhere near MTOW) and your acceleration will be reduced.Regards,Mark

>Not necessarily. >>When you are light, you can use thrust derates. On an >eternally long runway (something like 4000 meters) you can >enter a very high assumed temperature (provided you are >nowhere near MTOW) and your acceleration will be reduced. >Regards, >>Mark Good point, but factoring in derated takeoff options changes the whole basis of the problem statement.However, should we assume the use of thrust derates then at a lighter takeoff gross weight you might be in the equivalent performance regime as a higher takeoff gross weight w/o the derate - that is - a slower rate of acceleration as you approach Vr. The question remains ... but I'll rephrase.For a given EPR or N1 and following the Boeing recommendation for a 2 degree per second rotation that begins at Vr (without hesitation at 8 degrees nose up pitch):Is the chance of tailstrike greater at higher gross takeoff weights as compared to lower takeoff weights (for the reasons stated in the earlier post), OR, will the climb be initiated prior to tailstrike at all takeoff gross weights?And, once we beat this to death we can then talk about the longer 764... ;-)-michael

... you would exceed the V2+15 to V2+25 target airspeed window ...What would happen if this was exceeded? A lot of times I takeoff and shoot past V2+10 by the time I have finished my rotation, sometimes before reaching 300 ft AGL. I thought the faster you go, the better (safety margin from stall) and if she wants to accelerate, let her.

Well, you might exceed flap placard speeds. Or you would have to pull back sharply on the yoke and pull some Gs - something that the pax dont like :-)

Gents,I offer the following notes on tail strikes from company briefing notes for the 767.Take-off and initial climb performance (certification/obstacle clearance climb performance requires the airspeed to be V2+15 to V2+25) depend on rotating at the correct airspeed and proper rate to the rotation target atitude.As the airspeed approaches V1, the control column is moved to neutral or slightly aft of neutral. For optimum takeoff and initial climb performance, initiate a smooth continuous rotation at Vr towards 15 degrees of pitch attitude. With a consistent rotation technique, where the pilot uses approximately equal control forces to experience approximately equal seat forces, the resultant rotation rate will differ depending on airplane body length. After lift-off adjust pitch attitude to maintain the desired airspeed. Rotate smoothly at an average pitch rate of 2.0 deg per second for the 767-300. Lift-off attitude will be acheived in approx 3 to 5 seconds.Typical Takeoff Tail clearance (for Flap 5, 15 or 20 takeoffs): Lift-off Attitude Min Tail clearance Tail strike 7.5 deg 24 inches 9.6 degTakeoff and initial climb performance depend on rotating at the correct airspeed and proper rate to the rotation target attitude. Early or rapid rotation may cause aft fuselage contact with the runway. Late, slow, or under-rotation increases take-off ground roll. Any improper rotation decreases initial climb flight path.Tail strike occurs when an airplane tail section or lower aft fuselage contacts the runway during take-off or landing. The 300 series aircraft are more susceptible to tail strikes than the 200 series aircraft. Eight factors contribute to tail strike (some have to do with landing and I have not included them here). A significant factor that appears to be common is the lack of flight crew experience with the model being flown. Understanding the eight factors that contribute to a tail strike can reduce the possibility of tail strike during initial operating experience as well as continued safe operation as a more experienced flight crew.Mis-trimmed Stabilizer: This usually results from using erroneous take-off data (e.g., the wrong weights, or an incorrect C of G). In addition, the information presented to the flight crew may be accurate, but it could be entered incorrectly in the FMC or set incorrectly on the stabilizer. The flight crew can preventthis type of error and correct the condition by challenging the reasonableness of the load sheet numbers. Comparing the load sheet numbers against past experience in the aircraft can assist in approximating numbers that are reasonable.Rotation at Improper Speed: This situation can result in a tail strike and is usually caused by one of two reasons: rotation is begun early because of some unusual situation, or the airplane is rotated at an incorrect rotation speed that is too low for the weight and flap setting.Excessive Rotation Rate: Flight crews operating an airplane model that is new to them, especially when transitioning from an airplane with unpowered flight controls to one with hydraulic assistance, are most vulnerable to using an excessive rotation rate. The amount of control input required to achieve the proper rotation rate varies from one model to another. When transitioning to a new model, flight crews may not consciously realize that it will not respond to pitch input in exactly the same way as their previous model.Improper Use of the Flight Director: The flight director is designed to provide accurate pitch guidance only after the airplane is airborne. With the proper rotation rate, the airplane reaches 35 feet with the desired pitch attitude of about 15 degrees. However, an aggressive rotation into the pitch bar at take-off is notappropriate and may rotate the tail onto the ground.Whew! A long post, and it doesn't answer the mechanics questions, but some good gen on tail strikes.Kevin in CYOW

Quite simply, it comes down to this:If you have to wait at ~7 degrees pitch up, you did something wrong. Either you rotated to quickly (rotation rate), or too early for the aircraft configuration/weight etc. This could be caused by innacurate calculation of Vr. At whatever weight, atmospheric conditions, CG etc, a correctly calculated Vr will give you a non-stop rotation effort up to around 15-17 degrees or whatever necessary to maintain V2+15 to V2+25.If you rotated too slowly and your speed increases to more than V2+25, the flight director will guide your nose up to whatever is needed to get back to V2+25. No sudden or sharp movements are needed there.Iz