NG autolands

[Tan]

Just out of curiosity I read on another thread that “No Cat 1 ILS Autolands for the NG”. Is this a NG limitation or perhaps a company SOP? Seems strange that's all.

[BOAC]

Don't know the answer, but it is always wise to consider very carefully the problems in autolanding when you:-
a) do not need to and
b) do not have 'protection'

[notdavegorman]

It's not listed in the aircraft limitations section of our OMB, there is a statement to that affect in the OMA, with the caveat that Training Capts can for training purposes, together with a note stating caution must be used because of possible interference to the ILS beam due to the lack of protection when LVOs aren't in use.

[Tan]

notdavegorman

Thank you but I'm still puzzled as the 767 never had any cautions nor do the Airbus's.

[notdavegorman]

Just speculating here, it might because in the latter stages of an autoland approach, the 737 feeds in nose up trim (in case of g/a), and holds the nose down with noticeable forward motion on the control column, my guess is if the autoland had to discontinued for any reason, continuing the approach manually could be quite tricky due to the out of trim state.

[BOAC]

ndg - really no different to a dual-channel approach to 200' for a manual landing.

[notdavegorman]

...but not the case of a/c deviating from desired flightpath very late in the approach, let's say 65' RA, when one disconnects to make corrections, one also has to put in quite a lot of nose down trim. All sounds a bit unstable to me. As I said, just speculating.

Tan, do the 767 & Airbus apply nose up trim like the 737?

[Tan]

Sorry for the delay in answering your question all the aircraft that I’ve been typed on when doing auto lands trim nose up and depending on where a pilot disconnects probably requires a slight forward check pressure. In short the aircraft is out of trim. On CAT 3 the problem does not occur as the pilot does not disconnect until the end of the landing roll.

That said very few pilots actually ever use the autoland function except when they are mandated to do so as in a CAT 3. It’s just not a pilot thing to use the autoland as it spoils the fun of it..

[notdavegorman]

Well, bang goes my theory!

[Tan]

Well not really the aircraft can be slightly out of trim but nothing that a pilot can’t handle. I’ve also seen aircraft remain perfectly in trim so there are lots of other factors involved including the rigging of that particular airframe..

[The Real Slim Shady]

It comes down to Fail Passive and Fail Operational systems.

With 3 APs the system may, or may not apply some nose up trim, but a 2 AP system will apply some nose trim to allow for the disconnect if one channel fails. Apparently it assists with the go around, giving you a little extra time to react while the airplane ROD reduces.

[boeingdream787]

My 2 cents worth.Have a buddy in Boeing Seattle who writes the manuals we read.He says that sterile area incursions were so far and so few during manufacture and ops of the 767 and the 320's that this was pretty much of no consequence then.Now with such high density of air traffic,runway incursions along with protected and sterile area(in regards to the Loc/GP signals),have gone up significantly!! Boeing company....he says has NEVER ever restricted autoland on the 737ng except with a cautionary note during Cat1 ops wherein the sterile areas are not protected by vehicular/aircraft movment.This cautionary note too is to cater for the higher density of traffic during the 737ng manufacture and operations.......!!!ALL the above systems are quite fail safe but say,as NDG correctly put it,something mals at 65'RA.Would be very embarrasing for the company and Boeing.Therefore.....COMPANIES are now applying restrictions on their airplanes and their airmen.No probs with CAT2/3.Cheers all.

[alexban]

Indeed ,the caution is respective to the lack of protection for the ILS system on landing at cat I. I've seen this happen when landing shortly after departing traffic,you can get a sudden move of the localizer,very close to the ground.The plane,if on automatics,will try to correct for that,..not unsafe,but not so nice either.
It's no problem with the auto nose up trim,I've disconected the autopilot at heights from 100' to 30' ,no problem whatsoever.Actually,after Retard,the plane will land by itself,even if autopilot is disconected bellow 50'.No major control movement required from the pilot.