B737-300 Simulator Brakes Fidelity

[Tee Emm]

The local B737-300 simulator displays a very marked and quite alarming juddering from the hydraulic jacks when max braking is applied either on RTO, Max Autobrakes on landing or max manual brakes. The instruments become a blur due to the high frequency oscillation. Judging from the reactions of new pilots to the simulator it is quite alrming to them too.

The techs advise this replicates full anti-skid operation. I am sceptical about this as all the other 737 sims I have flown have never displayed such savage braking characterstics. I would appreciate views from simulator instructors and students who have had the occasion to use max braking on their simulators. Remember, this is not a mild judder associated with simulated anti-skid operation, but a wild ride of massive high frequency oscillation until the aircraft stops.

[CLbeta]

What is the certification level of the sim? I have heard that the RTO function on a real 73 nearly throws you out of the seat! Not sure about the juddering though. How old is the sim?
CL

[Tee Emm]

Level D in Australia which means all credits. In fact it is a first class simulator although I believe 1985 Redifusion model. It is just the savage braking that has me curious.

[belowMDA]

The RTO's I have done in our sim have never been accompanied by any vibration. Our sim is a late model 733 CAE 6 axis level D.
As an aside, about 12 months ago I did an rto from about 95 knots. No vibration and the braking was savage. Had to peel myself off the instrument panel!

[CLbeta]

Aviation authorities can make realism concessions to older sims (20 years +), due to technical limitations of the machine. This means that an older, less advanced sim, can be still be rated at the same level as a more capable new sim. New sims have self diagnostic utilities which, can flag a problem in relation to motion fidelity.

A sim built in 1985 might not have the ability to self diagnose motion fidelity issues thereby, missing a motion fidelity problem for RTOs. If a few of your colleagues agree with your claim, then have a chat with the sim manager, see if he/she can get a simulator engineer to take a look at it for you,

CL.

[lefthanddownabit]

I don't know about the 737-300 specifically but on some aircraft antiskid does cause noticeable vibration. Although this is not part of the designed motion buffet model, nor is it on the list of buffets explicitly required, it is sometimes added as a local mod as a result of FAA, CAA or CASA "requests for improvement".

It might be a motion maintenance issue. The simple way to test would be to do an RTO with the anti-skid off and see if the vibration still occurs. If it doesn't, it has been added to simulate antiskid vibration as the sim techs say.

[PPRuNe Pop]

I was recently in a 300 at Dallas and I didn't notice that at all. The CI certainly didn't mention it either.

[Tee Emm]

Thanks for your replies which are greatly appreciated.