Fidelity of B737NG simulator

[A37575]

Engine Failure at V1. A certain Alteon B737 simulator 26K engines not only needs full rudder for stable heading single engine climb at V2 but also requires significant aileron control to maintain heading. Without this aileron input the simulator steadily yaws into the dead engine even with full rudder. In addition, when flap lever selected from flap5 to flap1 as part of acceleration process the rudder gives a noticeable "kick. Is the fidelity of the simulator suspect - or is the running out of rudder control ops normal at V2?

[Dehavillanddriver]

That particular sim is currently the subject of much discussion between various parties with the technical people for the airline that uses that sim exclusively argueing that there is a problem.

I suspect that you may see some improvements over time, the person who is following this issue is a tenatious individual (and a good guy) who will make sure that when finished the sim will match the aeroplane - he used to be a test pilot in another life so is used to sorting these sorts of issues out.

[A37575]

Thanks DH Driver. Seems the Qantas NG has identical problems, too.

[212man]

So how did it meet the QTG and receive a certification?

[gimpgimp]

In our 800 sim there is a slight kick on the rudder as the flaps are retracted and reach the UP mark on the flap gauge. I offer info from my airline’s training department below and assume the real aircraft also has this kick. Will keep looking for more info. Is there someone out there who has flown real a aircraft engine out clean up during testing that can confirm?


“A number of reports have been received regarding the different flight characteristics observed when flying the 737-800 simulator. The discussion centers on the different amount of rudder pedal input required when maintaining a constant track. This at times requires full rudder input accompanied by some aileron. In short, the 737-800 simulator is performing as per the aircraft. The objective data has been confirmed as correct along with subjective assessment also confirming that the simulator reflects the aircraft. It is important to not just convey but to emphasize the difference between the 737-300/400 and the 737-800 aircraft during training. The difference in flight characteristics is mainly due to the Rudder Pressure Reducer in the 737-800 compared with the 737-300/400. When an engine fails on the 737-300/400 the full 3000 p.s.i. is being delivered to the rudder PCU whereas the 737-800 reduces hydraulic pressure to the PCU when the aircraft passes above 135 knots. In essence the 'blow back' effect on the rudder surface deflection is greater on the B737-800 and results in less rudder surface deflection compared with the 737-300/400. To the pilot the result is more rudder input is required under identical flight conditions. The 'blow back’ effect will be exacerbated if over controlling and sideslip occurs, sideslip will further reduce rudder surface deflection and if rudder pedal input has reached it's maximum more aileron may be required to retain the required tracking. Only very specific and rarely encountered conditions require aileron input. Less than ideal pilot performance may also require the use of aileron in addition to full rudder input. The requirement for aileron is more likely where the departure procedure requires an immediate turn after take-off. The 'spongy' feedback through the rudder pedal is simply replicating cable stretch. This is a new experience if full rudder pedal displacement has not been experienced. This issue could impact the training value to pilots if the different characteristics are dismissed as being a result of poor fidelity rather than a true reflection of the aircraft performance. If the crew believe it to be an inaccurate reflection of the aircraft it downgrades the effectiveness of the training too generally and fails to prepare the pilots for the reality of the aircraft. “

[AirRabbit]

Hey Guys:

While I understand what gimpgimp stated in his post, dealing with the installation of a rudder pressure reducer that dropped the hydraulic pressure assisting in the displacement of the rudder surface with a given amount of rudder pedal deflection, I disagree that such systems are only in B737NG aircraft. I think that if you go back and check the history of the B737, you will find that about 5 or 6 years ago Boeing mandated a change to the rudder system in all B737s. It came after a long series of discussions and finger pointing after the second fatal crash of a B737 (landing approach at Pittsburgh, PA, USA - the first one was in Colorado about a year or two earlier). At the same time, Boeing issued a “data update” for all those who operated B737 simulators around the world. There was a lot of discussion between some of the regulatory authorities and the engineering offices at Boeing (both engines and controls) to be sure that what was being provided was going to result in the proper indications in the simulator(s) – i.e., that the simulation was an accurate replication of the performance and handling of the respective series of B737.

I don’t recall the trigger for this pressure drop (either airspeed or altitude or a combination) in the earlier series of B737s, but if a pilot had the rudder pedals deflected to “almost maximum” (Boeing engineers’ phrase) at the time the rudder pressure was reduced, the pilot WOULD feel a “nudge” or “kick” in the rudder pedals. These engineers also indicated that if normally required rudder pedal deflection was being maintained, the pilot would likely not feel anything in the rudder pedals when the pressure was reduced, even though the rudder surface itself would change to a lesser-deflected position. This was because there is no direct connection between the rudder surface and the rudder pedals.

However, after having said all this, I also believe that if anyone has any concerns about the fidelity of the B737 simulator (or any simulator for that matter) that person should write up the concern in the simulator maintenance logbook and demand a correction or an explanation. And further more, if such a correction or explanation were not forthcoming, I’d recommend taking the situation to the regulatory authority.