Normal Pilot Reaction Time
 

Anybody know or know where I can find a definition of this JAR term, please? Trawled through JAR but not found explanation. Not listed in the Definitions section.

Multp

I don’t have an answer to your question, but when you do find a definition I shall be very interested to see what it says!

o My first thought is reaction to what?

o A light coming on which you are waiting
for with your finger already on a button
to indicate your “reaction” (my guess
0.2 sec or less)

o An unexpected big bang (my guess 1 sec
plus)

In my day Boscombe insisted on a two second delay before taking action to show that an aircraft could be controlled following a failure such as autopilot/autostab hard over or an engine failure. (my feeling is that was not a bad every day assumption for a totally unexpected event happening during routine flight)

Surely a guy about to launch off a catapult at sea (for example) is in a different state of arousal to a skipper turning to welcome a visitor to the flight deck two hours into the cruise. And there must be quite a few states between such extremes.

JF

The only place I've seen a clearly defined reaction time criterion is in the critical engine failure case for multi-engined aircraft in JAR/FAR-23, there's no such reference in JAR/FAR-25. My feeling is that this is probably because the case is far more critical in a lighter aircraft.

JAR/FAR-23 requires that with flaps and gear up, MCP and propellers set for climb, it must be possible to fail the critical engine at any speed down to Vmc, wait 2 seconds (the defined reaction time), and then bring the aircraft back under control without seeing more than 45° of bank.

JAR/FAR-25 don't define a reaction time, presumably leaving it to the test team to decide what is appropriate, but are stricter in requiring a maximum of 5° of bank and a 20° heading change without using more than 150 lbf rudder force.

However, going back to JF's comments, there are all sorts of cases (single engine aircraft engine failure in a steep climb for example) where it is necessary to determine a pilot reaction time and use it during certification. In my experience 2s is pretty much universal in civil certification, presumably because the figure already exists in one context.

If you go back 30 years and trawl through either AvP970 or BCAR Section D, which I image were set texts when JF did his ETPS course, you'll find that they were much more prescriptive about such things than modern practice, and you'll probably find a lot more wisdom there. On the other hand, BDN has a long track record of not even reading the standard and simply applying common sense.

Another source is Donald McClean's book "Automatic Flight Control Systems", which defines response control laws for pilots at different states of ability and alertness. Where he got them from I don't know, but he's still a professor at Southampton University, and I imagine would be glad to talk about it if you phoned him.

G

[This message has been edited by Genghis the Engineer (edited 29 April 2001).]

Thanks, chaps. If you look at 'Rotorheads' topic Autorotation you'll see I've chipped into that debate. I was at work at the time...paradoxically without my tps notes, with which I have now refreshed my memory.
I don't have BCAR here, but my extracts from 00-970, which refer specifically to (rotorcraft)FCS failures strike the odd chord. Furthermore, the 2 seconds for engine failures is cited as the 00-970 requirement 'as a realistic reaction time for the average pilot to identify a total power loss under unfavourable conditions and then to lower the lever'; 'active'response time is 1 sec but 'attentive hands on' pilot response time is given at 1.5 secs.
The JAR requirement for engine failures is given as 1 sec 'or normal pilot response time, whichever is the greater'. Mmm, very useful if normal PRT is not defined!
Since JAR are very close now to FAR, I suppose the FAR standard may be followed.
Incidentally , on the subject of 'lever delays'in the R22 even a planned 1 sec delay in the climb at 60 KIAS was, to say the least, exciting.....
Any more comments, please?

I'm bemused that the JAA considers RW pilots only need a second to respond to an engine failure, yet FW pilots take a leisurely 2 seconds.

Possibly a fudge to allow certain helicopters with low rotor intertia to pass certification perchance?

G