I fully endorse
John_Tullamarine's remarks with respect to excessive trust in simulator fidelity, as compared to 'real aircraft' data. Typically, simulators are programmed to provide a reasonable representation of the aircraft's flight characteristics within the normal flight envelope, with little attention given to charasteristics outside the normal envelope.
The normal envelope considered for simulator fidelity is from stick shaker at the low speed end, up to Mmo at the high speed end. Within this band, simulator response can be considered as quite reasonable, outside the band, most of the data is simply 'off the shelf' generic code applicable to most aircraft. Pilots are trained to respond to the stick shaker and overspeed alerts appropriately, and, as a training tool for normal operations, little attention is usually given to flight characteristics outside this band.
I have had some insight to how in-flight test data is incorporated into simulators, having done flight testing, and taken the resultant data onwards to the simulator (usually on the same day). A lot of it is 'hard' data, but a lot of it is the testing pilot carrying over his own subjective response to the simulator programmers.
On one aircraft type that I did this for, the launch customer for the type wanted to incorporate some realistic data beyond the normal range, as this aircraft was to be the operator's junior aircraft where trainees would be exposed to their first jet aircraft. In achieving this, I am able to provide the following general summary -
(1) Up to Mcrit, control response is conventional, i.e. with increasing speed, the aircraft tends to pitch up, and forward elevator and trim are required to maintain stable flight.
(2) Mach Tuck begins to manifest itself after Mcrit, in the initial stages it is rather mild. The aircraft continues to pitch up due to increasing speed, but Mach Tuck begins to counterract this. At or about the Mach Number where the pitch up and the pitch down forces are equal, the "MACH TRIM INOP" speed limit is imposed. Full elevator authority (or close to it) is available. This Mach Number is usually about 0.02 above Mcrit,
BOAC has indicated that the "MACH TRIM INOP" limit speed for the B737 is M0.74 (reinforcing my assertion that Mcrit is about M0.72 for the B737).
(3) Beyond the "MACH TRIM INOP" speed, the Mach Trim system progressively makes greater input. The upper limit of allowable Mach Number is determined when UP elevator authority (without assistance from the stabiliser) is at a point where just sufficient is in reserve for recovery. MMO is established about 0.02 to 0.03 below this speed. (It must allow for Mach Trim fail right up to MMO and the aircraft recoverable, with an elevator authority margin, using Elevators alone).
(4) Beyond the upper limit speed (MMO + 0.02 to 0.03), elevators alone cannot effect recovery, and UP stabiliser is required to regain control in addition to Elevator input.
SR71 has indicated this in his last post. For certification purposes, the aircraft must be able to recover without resort to stabiliser use. In a MMO exceedance case, where elevator control is insufficient, stabiliser use is imperative. Our flight testing terminated (to my relief) when we had passed the threshold where stabiliser use was necessary for recovery. As our simulator response was quite realistic in the area of MMO exceedance (proven), crews were taught the absolute necessity of stabiliser use to effect a recovery. The secondary unpleasant aspect of this was that as the aircraft then pitched up and reduced speed, it was trimmed well nose up, often (always) resulting in a large zoom upwards requiring down elevator and assertive forward stabiliser trimming.
Centaurus, the Silk Air B737 was supersonic, although I do not know to what degree.
BOAC has come up with some good info here, I agree with him that the first portion of the B707/B727/B737 to pass mcrit was the nose/cockpit region, probably also the case with other aircraft too. Although increasing drag will always be a concern to us, increasing control problems are of far greater concern, and thus, Mcrit is typically quoted for the wing (even though other non-control portions of the airframe have already passed M1.0).
Getting back to simulator fidelity, modern fly by wire aircraft normal responses are very well emulated in the simulator, as the same computer/commands/logic of the Primary Flight Control (PFC) system is used in the aircraft and the simulator. When we turn the PFCs off during training, the same old "is it real?" question arises.
We never did get the low speed end of the envelope right, the simulator stalls like a Tiger Moth, but the fully developed full back stick stall in the aircraft is a wildcat!
Hachiouji-shi, I can't help but think that you're confusing Mcrit (a mild encounter) with the very adverse effects of gross MMO exceedance
Regards,
Old Smokey