Auto Take Off

[trium16]

Hi

I tried searching the web for information on two topics that have been puzzling me for a long time (but had no success, maybe you guys can help).


1) Does any Commercial Airliner have an auto takeoff facility? Somebody mentioned the L1011 to me once (it wasn't the guv either!).

If not, why not?

2) I read a book once, perhaps it was "handling the big jets", however I recall the published date as 1974.

This book had some pics inside the cockpit of a BOAC 747-100/200, and in between the pilots just in front of the throttles was a very large vernier type dial named "SLEW" - what did/does this do???

[Golden Rivet]

Not that I know of - most autopilots can only be engaged after a specified altitude has been attained ( eg 400 ft ).

As always I'm happy to be corrected.

GR

[fatboy slim]

2) I think SLEW would be Yaw Trim in today's money.

[QAVION]

"Not that I know of - most autopilots can only be engaged after a specified altitude has been attained ( eg 400 ft )."

Depends on the mode, GR, and, of course, the aircraft.

I have had no problem engaging HDG HLD, HDG SEL, V/S and FLCH on a 747-400 on the ground. Theoretically, you could use FLCH for takeoff, if it wasn't so risky doing so (I believe someone has already tried this, anyway, in real life and got away with it).

Yaw control would be another matter. It's not engaged until the aircraft is in the air (plus or minus a few seconds).

Autotakeoff is achievable, technologically, but it carries a lot of risks. You would probably need a computer like Deep Thought to consider all the things that could go wrong and then take appropriate action... something which the pilots have already mentally prepared themselves for before they push the TOGA button.

Regards.
Q.

[AhhhVC813]

I believe Airbus were looking to introduce an auto take-off mode on the 340-500/600, but couldn't get the agreement of the airlines who had ordered them.

[Cornish Jack]

trium 16
I think that the L1011 reference was partly correct. If memory serves me correctly (not very often, nowadays :( ) Lockheed included the ability to take-off with Control Wheel Steering engaged. This was a limited autopilot function which allowed manual input to override the A/P stabilising function in pitch and roll and allowed altitude capture.
I don't know of any operator whose OM allowed this function to be used for take-off.
As in most areas, the L1011 was light years ahead of its contemporaries.:ok:

[*Lancer*]

I heard they're looking at it quite seriously for the A380...

It's not that hard to do - apparently Boeing have already admitted it's only a minor modification to the autoflight suite to get it going (hell, enough drones do it already). Auto-Rotate pitch mode, and Rollout (or similar) isn't that complicated - even with an engine out. QAVION, there are a lot of considerations, but like landing, even if you get a No-Autoland you can still take manual control without significant consequence.

The alternative is if the automatic feature simply just controls the elevator to avoid scraping the tail...

I really hope the insurance companies realise the overwhelming negatives of mandating auto take-off and landing!

Lancer

[Larry in TN]

What's the point?

Autoland makes sense because it allows you to land in lower visabilities. What would auto takeoff give us that would justify the expense of the equipment, training and maintanance?

[B73567AMT]

Software in the FCCs on the B737 and B757 prevent Autopilot mode engagement for takeoff. Yes Hdg Sel and other modes can be selected on the gnd, but they are not available once the A/P is put into Takeoff mode (TOGA). The modes are inhibited until 400ft AGL.
Go ahead try it, it can't be done.:p

[QAVION]

"Yes Hdg Sel and other modes can be selected on the gnd, but they are not available once the A/P is put into Takeoff mode (TOGA). The modes are inhibited until 400ft AGL."

Not sure I understand this, B73567AMT.

On the 737, if you have, say, Level Change and HDG SEL engaged (CMD) on the ground, will the TOGA switches do anything? I assume these modes would override the TOGA arm modes(?)

Also, on the 757 with, say, HDG SEL/FLCH engaged on the ground (if possible), I also assume TO/TO won't be annunciated. Would pushing the N1/EPR button change change the FMA annunciations? If so, could you bypass this by pushing the thrust levers forward manually?

Thanks.
Regards.
Q.

[B73567AMT]

I'll backoff the 757 until I can find my material...but on the 737, it is written in the software that TOGA will cause the A/P to disengage.
I have to find it in the algorithms, but I know it is there for a fact.

[OneDotLow]

With respect to autoland.... the AFDS uses the LOC signal to align the aircraft with the runway, then takes a snapshot of the ground track just prior to annunciating rollout as the active mode.

My question is... how would the aircraft know what track to manouver the a/c on for a takeoff.

GPS? Maybe, but I dont think that this can be relied on to give an accurate enough position.

Having said all of that, maybe in the computer control laws (like the 777 has), there could be someting added to minimise tailstrikes... just a thought.

[NigelOnDraft]

As alluded to above - WHY?

Autoland (with close pilot supervision) was only designed and implemented to get around a weather problem... i..e for commercial reasons.

I see no commercial advantage to "auto-takeoff"...

At a practical level, probably far easier than autoland to implement... but if it requires the same level of pilot supervision as autoland, why not just get the pilot to do it?

NoD

[Zagor]

I see potential hazard like tire temperature,long taxies brake temeratures that could effect the T/O performance, the main reason why is not necessary to improuve safety by automation.

however is uncleas to me why in autoland there are no implementation of the Flap and gear extension performed according to FMC speed.

It will bring safely down as plane with total incapacited crew.

[Ignition Override]

To add to what Nigel O.D. and others said, more automation during the most critical phases of flight does not mean that more safety will result, and probably much less. It often disappoints/dismays me to read that more layers of technology will always be pursued if tiny savings in operating costs can (in theory) be achieved. Our upper mgmt would let us fly airliners solo if the FAA and insurance companies could find it legally and financially feasible.

The Airbus (begun with the fly-by-wire 320 series) design philosophy seems to put much less faith in pilots (or their experience levels with some operations?) than Boeing's automation philosophy. Many of our pilots have flown both types of products.

Do most aircraft design engineers, in a general sense, look down on human pilots? If so, then it is doubtful whether very many of them have much IFR experience in a real airplane. A concept is one thing, but experience and some judgement can not necessarily be digitized, prioritized and programmed, can it?

[NigelOnDraft]

Zagor

<<It will bring safely down as plane with total incapacited crew.>>

I'm afraid you are completely missing the point. You seem to think Autoland is controlled from the ground, and/or the pilots set it all up in the cruise or something.

All Autoland does, and all it is designed for, is provide a mechanism to get around the problem of poor visibility in the last 200'.

If you are looking for a solution to the "incapacitated crew" issue, you are opening up a totally new can of worms... and lowering Flaps and Gear is the most minor of the concerns that would need to be addressed.

Even on the Airbus, an Autoland, safely conducted, involves extensive crew interaction and systems monitoring. There is even a half page of "deficiencies" that limit or prevent Autoland that are not monitored by the aircraft systems...

NoD

[PAXboy]

It often disappoints/dismays me to read that more layers of technology will always be pursued if tiny savings in operating costs can (in theory) be achieved. Having worked in technology for 23 years - I heartily agree!

Bean counters will always opt for fixed costs over flexible i.e. equipment against humans. They can plan for fixed costs with purchase, depreciation and (so a fair degree) maintenance, across ten years. Humans make unplanned demands and may resign, go on strike or experience long term illness, needing contract (expensive) replacements. Worst case, ccxd sectors. With a box, you go and buy another one and if the maintenance costs rise, you change the maintenance supplier. Ensuring, if at all possible, that if the new lower cost maintainer makes a mistake, that he will pick up the liability of a claim.

Last week, I was in a meeting of a very senior and experienced engineer (not aviation) and he said, The accountants optimised the hell out of everything and then they got bored. So they decided to run the companies as well. Now we're all in trouble.