Viscount loss of Control.

[Nigel H-J]

Have put this here as was on a VA Flight from Heathrow to Jersey when around 20 minutes into the flight cruising at FL120 with auto-pilot I left the flight deck - on my return the Viscount was turning nearly ninety degrees and descending fast!! disengaged auto-pilot but no matter how much I tried with the stick she would not recover until I reached 3900ft but even then control stability was terrible, re-connected auto-pilot but again the aircraft went into a gradual left hand turn, selected manual but did not have full control and she went into the Channel!!

Never had this problem before so have had to abort the flight.

Will try again shortly but has any-one else experienced control problems with the Viscount though this is the first time it has occurred to me, any ideas? BTW not joystick problems.

Nigel.

[DaveB]

Hi Nigel..

Glad you managed to save the passengers by aborting before impact I've never had this problem and I've never seen it reported which leads me to the only thing I can think of.. did you have real weather on?? My gut feeling is that you've hit sever windsheer and as you weren't there when it happened, the aircraft has had no chance to recover. Only ever had this happen once and it wasn't on a VA flight I'm glad to say. I was taking a C1K down to ASI.. left it as you did with yours and came back to find I was heading for Canada!

ATB

DaveB

[TSR2]

I've had this problem in tha past, particularly on the Vanguard which has a similar style auto pilot, even in the default good weather you can hit what appears to be a pocket and if your not athe the controls your stuffed.

[Garry Russell]

I did have this in the VC 10 and when it occurred noticed the wind reading was all over the place which seems to tie in with DB's theory

[Nigel H-J]

I was taking a C1K down to ASI.. left it as you did with yours and came back to find I was heading for Canada

Thanks for your replies, I just had default weather on set at 8/8ths cloud with rain, going try again and hope none of the passengers want a refund before take-off!!

Never had this before with the Viscount before though when I initally got control back she did not seem to want to respond with the ailerons so in effect it initially appeared to be lateral control problems and as you know, the secondary effect of ailerons is for the nose to descend as the top wing tries to keep up with the lower one.

Back to the Viscount to tryt again.....BTW, any-one volunteering to be co-pilot?

Regards
Nigel.

[DaveB]

No Sir

It may be that the AP fought whatever it was it hit and trimmed itself out of the sky trying to hang on mate. Your attempts to rectify the problem would've been fruitless in a completely out of trim aircraft. Anyway.. make sure you go for a 'toilet' BEFORE you takeoff this time or at least hit the pause key until you get back

ATB

DaveB

[Nigel H-J]

Anyway.. make sure you go for a 'toilet' BEFORE you takeoff this time or at least hit the pause key until you get back

Point taken Dave though it was to make a cup of coffee, just can't get the cabin staff these days!!

Presently 60nm from Jersey though it will have to be an overnighter there and return tomorrow, must have been what you all suggested earlier and with the auto-pilot trimming itself out of the sky as Dave said, would certainly be the answer why I could not regain control......pity I did not think that out logically but there again, just goes to show what the brain misses in an emergency, another learning curve completed.

Again, many thanks and Jersey......Here I come!!

Regards
Nigel.

[cstorey]

How accurately does the model and/or the weather engine model icing? Both the initial upset, and the failure to be able to recover, sound rather typical of control and/or aerofoil icing, and the conditions you describe are highly conducive to the problem in the real world

[Buggyman]

Had a similar event a few years ago when flying a DC4, 6 or 7 on a ferry flight. Left it on autopilot to get a coffee & sandwich and when I returned the aircraft had ditched in the North Sea. Restarted the flight from the beginning and waited to see what happened and at exactly the same point the aircraft began a slow left turn - with autopilot still on - which increased in intensity until hitting the deck.

On the third flight - yep I've either got lots of patience or time to spare - I noticed that the fuel selector was set up to take fuel from one wing. My guess was that the aircraft gradually became unbalanced enough to overcome the autopilots control. Anyway, the final flight with the fuel monitored all the way was ok.

Just my ten penny worth....................


Allan

[DaveB]

Fraser modelled the panel so that it will fall from the sky anyway if you don't have the PUD's turned on. Some of his panels you can cheat/workaround.. the Viscount is not one I've seen strange things happen to the ASI regardless of pitot heaters being on so FS does get confused from time to time.
Unless Nigel really cocked up.. he shouldn't have had a fuel imbalance. A short flight like that wouldn't have needed the outer tanks so he would have had to have inter-engine cocks on and the outer booster pumps off in order to get rolling (the VA software loads the inners first and if anything was in the outers.. going from fuel to no fuel in less than a second cuts the outer engines). There IS crossfeed on the Viscount to counter any fuel imbalance but in the virtual world.. this should never be needed. There's always finger trouble
When I had the incident in the C1K going down south.. I redownloaded the same weather and x16'd the flight until I got it to an approximate position for the previous anomaly. Bless my soul if it didn't do it again.. severe windsheer, aircraft blown completely away from it's course and ASI frozen!! This explained why I found it heading toward Canada at leary speeds running out of gas Of course, on the second occassion.. I completely disconnected the AP and flew out of the cr@p by hand. The ASI eventually cleared when I'd got low enough. Fortunately.. I suffer no such problems in the Rapide

ATB

Dave