I just landed in the Queen in heavy blowing snow, -10C, at BIEG, Iceland on a short runway and pulled on the reversers after doing an autoland and....no reversers, arghh! I skidded all the way down the runway to a halt 6000 feet later.I tested things afterwards and found that if NAI is ON at touchdown (and I had it on for descent in this dreadful weather), then the reversers do not activate at all; but if NAI is switched OFF, then the reversers do work normally. Is this normal (or is it just me?)?Jonathan

It's a bug, and I don't believe it's been fixed. Be sure to turn off NAI when on final.I've copied a message from Robert Randazzo, below:- Bill"John- Thanks for your report.... I just ran a few tests and you may indeed have found something legitimate! Here is what I believe to be happening: 1) NAI draws bleed air from the engine to provide heat energy for the nacelle duct. In order to compensate for this drain on power- and the effects of slower spool times when the engines are at idle, the EEC's command a higher idle thrust level in order to ensure regulatory guidelines for engine thrust transition times can be met. 2) It **appears** currently than in this condition, the higher idle thrust is creating some noise in the idle power sensor logic for the reversers... Thus the reversers are receiving erroneous commands to close... Currently this is an assumption- I'm still researching.... But it gives you an idea how complicated this airplane simulation is. Try this for a fun time: Select NAI for engines 3/4... Then select full reverse and take your finger off the F2 key... Oh dear... Manufacturers service bulletin coming...._________________Captain Robert S. Randazzo Precision Manuals Development Group"

OK, thanks. Good to know it's not me (!)Jonathan

Gents-I just put a fix for this into the latest 747-400X beta cycle. Hopefully, our testers will verify that it works properly.

I just did a short flight, actually trying what Robert suggested:Turning on NAI 3/4 on landing and all if my 4 reversers worked properly.Only erroneous thing I noticed was when in a stopped position, then the reversers where NAI is on, would close after releasing F2.