There have been several reports over the years of incorrectly placed cargo in the cargo holds that resulted in an initial difficulty for the pilot to rotate at VR. This shows out as nothing happens when you start the rotation and it seems if the nose-wheel is not coming off the ground. Usually if you heave more strongly on the wheel the aircraft (737) gets airborne and once into the initial climb use of stab trim corrects the nose heavy situation. I recall a recent 737 incident at Manchester where the F/O perceived a stuck elevator during his attempt at rotation and called to the captain to take over. The captain perceived the same difficulty and promptly aborted some time after VR speed. Fortunately they were able to stop in time. If I recall correctly the problem was the stab trim had not been set correctly and thus stick forces on rotation fooled both pilots.
I had a similar situation decades ago when the load had not been distributed correctly (unknown to me) and at VR despite heaving back literally the nose wheel stayed in contact with the runway. Another firmer heave back got the aircraft airborne around V2 plus 20 knots but not before a check captain in the jump seat actually panicked and screamed for me to rotate. I kid you not - the silly blighter frightened the heck out of me more with his shouting, than the delayed un-stick. At the subsequent court of inquiry held in the chief pilots office with tea and bikkies not supplied, I was accused of "forgetting" to rotate. Office politics was strong in that airline - but enough of that.
In fact, when we landed a few hours later at destination and weighed the cargo and checked its true distribution, the stab trim setting which should have been set (as against what we had worked out for the assumed distribution) was only around one unit difference. But the stick force to rotate was far harder than I ever would have thought.
There had been a similar, but far more potentially dangerous event, in a company 727 that refused to respond to elevator input at Vr. The pilot hit the stab trim and managed to claw his way into the air. Turned out the load had been understated on the load sheet by several thousands of kgs and the CG was outside the forward limit.
It got me thinking that where there is difficulty in rotation, it could cause the pilot to think the elevator had jammed. Things happen so quickly. In turn he may be tempted to make an instant (but possibly unnecessary) abort and by then V1 has long since passed and likely V2 as well.
For some years now, I have briefed pilots undergoing type ratings on the 737 of this insidious danger of incorrect stab trim setting which may cause a stick force reaction at VR.
In the simulator I operate, it is not possible to alter the CG enough to cause a significantly nose heavy stick force on rotation. I believe however, the possibility of this type of event happening once or twice in a pilots career is probably quite high.
But in the simulator how does one "fake" the stick force so that an actual very heavy pull back on the control column is needed to get airborne - apart from the obvious one of having the PNF push forward on the wheel while the pilot tries to pull back. It is all very well recounting on what could happen one day, but a picture or demonstration is worth a thousand words.
Now this may invoke snorts of derision from readers but one method to set the scene is by winding the stab trim fully forward before take off in the simulator. Of course the crew are briefed it is a training exercise with no surprises. The aurul warn C/B is pulled to silence the configuration warning. At Vr the pilot will find the initial pull back has no effect and the aircraft stays on the runway while accelerating well beyond V2. A strong smooth heave will eventually lift the nose and the aircraft gets airborne. Rapid operation of stab trim back to normal setting occurs in the climb and the lesson is over.
The object of the exercise is to have the pilot experience very heavy stick force at VR and still get airborne - rather than risk an instant gut-feeling decision to abort because of a perceived "unusually heavy stick force". I appreciate this may be considered a highly non-standard way of doing things. But one thing is for sure, and that is the resultant stick forces were identical to that I experienced during my incident in a 737 many years earlier. Necessity being the mother of invention, perhaps?
Comments invited of course but preferably constructive rather than derisory.
Maybe some expert can offer another solution how to introduce a very heavy nose heavy stick force in the simulator at VR but using normal take off stab trim setting. I believe it is an important part of type rating training.