View Full Version : T/O Throttle Settings

18th Apr 2002, 05:23
Hi, I wasn't sure where to post this since I am not an airline pilot yet, but I think this is the best forum. I have jumpseated a few times on the airline I work for, and I have watched a few of the www.justplanes.com inside the cockpit videos. I am wondering, on every 737 takeoff that Ive seen (maybe other types too, I can't remember), the captain will set TO power. While he is doing this the FO has his hand on the base of the throttles almost helping the Captain push them up. It doesn't seem to matter who is PF or PNF. Is there a reason for this? Aren't the TOGA buttons for this purpose? Thx, a wondering aspiring pilot.:)

18th Apr 2002, 06:38
In the good old days, before autothrottles, the pilot flying would advance the power to begin the take-off, and call something like "Set Thrust".

The pilot not flying would then fine tune the thrust to the calculated take-off setting, which takes a few seconds. This allowed the pilot flying to concentrate on steering the aircraft down the centre line of the runway.

More tradition than anything else on an autothrottle equipped aircraft - a manual backup, if you will.

18th Apr 2002, 12:08
Autothrottle has been known to do strange things from time to time. The FO's hand at the base of the throttles will ensure that an unwanted power decrease given from the autothrottle will immediately be recognized. :eek:
This in addition to monitoring the engine instruments, of course. Which are, by the way, the only source on an Airbus, as their thrust levers are not moved by autothrust... :D

18th Apr 2002, 20:50
throttles are fitted to cars.

the reason for the other pilot to stick his/her mitts behind the levers is to prevent the levers moving backwards during the acceleration on take off.

fly airbus: no need to do any of this - they are in a gate.:p

Cornish Jack
18th Apr 2002, 23:02
Just a little point, Checkboard.
On the 74/400, the autothrottle goes to Throttle Hold at 80kts [B]IAS[B] . If you do a rolling take-off into a strong headwind, with a slow throttle servo, you COULD find the throttle going to hold before the power is set. PNF would then need to trim them up. ;)

18th Apr 2002, 23:20
Additonally, another reason for the follow up is: if using a reduced thrust setting for take off the PNF will, on detecting an engine failure after V1, advance the remaining throttles to full take off power, particularly helpful on a limited runway/restricted climb out.

19th Apr 2002, 00:25
True enough, Cornish Jack, it is the same on the 73, but I haven't seen it happen.

Mr. Khan, that is airline dependant, some operators leave the reduced thrust set.

Willit Run
19th Apr 2002, 00:27

I pushed many a THROTTLE forward forward on DC-6's and Convairs! Those are real airplanes!
Also, not all Airbuses have those little detents, some of us are still capable of setting our own power!

Have a great day!

19th Apr 2002, 02:12
Willit Run,

That makes you a REAL pilot :cool:

19th Apr 2002, 10:32
Yup Checkboard, I should have been more specific. It would be a captains call but with his hand there the PNF would quickly increase to higher thrust, well that was the theory, Heston 1976, BAC1-11!

Flight Detent
19th Apr 2002, 11:01
Just to add a little more spice to your T/O power setting -
On the '74 Classic, it's the FE who follows-up with the power levers, and calls 'power set' and calls 'throttle hold' (when indicated), and increases the thrust on the PFs call during an engine failure on T/O.
Also, be aware, if not already so, with these types of auto throttles, if the T/O is aborted prior to 'throttle hold' indication, and the power levers are retarded to idle, the auto throttle system will continue to try to advance the power, very quickly, when you remove your hand from them, and that can be very embarrassing indeed.
The fix, always disconnect the auto throttle when you retard the power levers during an abort, one less thing to think about!

19th Apr 2002, 21:36
ok,I should have specified MODERN airbuses.

detent: how is T?


20th Apr 2002, 03:29
Willit Run. Throttles are for cessna 152's.....it's Thrust Levers for me. Full manual setting? I'd still prefer my autothrottle to set the thrust for us! We'll just glance and confirm setting of fine tune after 'throttle hold'. But yeah, I agree, none of this Flight Detent airbus stuff... ;)

Ford Airlane
20th Apr 2002, 03:46

B744 - HOLD mode for the autothrottle is activated at 65 KIAS, not 80.

It would have to be one bitchin wind for the power not to have reach the thrust reference limit by 65 knots!

Timbotch, yes that is what the TOGA buttons are for. Standard practice is to manually advance the thrust levers slightly to get the thrust coming up symmetrically. For Rolls-Royce engines thrust is advanced to 1.1 - 1.2 EPR, GEs I can't remember, but around 55% N1 sounds familiar. Once you are happy you push the TOGA button and the thrust levers advance to the thrust reference limit, which can be different for every takeoff depending on environmental conditions, runway and whether de-rated thrust is used.

To prevent what radarcontact alluded to with the autothrottle doing strange things (such as bringing thrust back to idle :mad: ) at really critical stages of the takeoff, another autothrottle mode activates at 65 KIAS (B744). This is called HOLD mode and the autothrottle does not actually control thrust and the thrust levers can be positioned manually (not usually necessary). I can't remember exactly when HOLD mode is de-activated and THR REF re-activated, it may be when VNAV arms or it may be one of those nosewheel extension +25 seconds or 400 feet whichever happens first things. Can anyone clarify that?

Flight Detent
20th Apr 2002, 11:51
Hi Fantom,
T's fine, where do I know you from?
email me!

Cornish Jack
20th Apr 2002, 12:03
Ford Airlane
Of course! :o The moral - connect brain and typing finger ! :D - the 80 kts was the other part of the requirement... that power must be set BY 80 kts.
QNH 1013
Ever the pedant... should that not be Autothrust?? :p :D

21st Apr 2002, 05:57
ha ha ha, you got me there. However my Boeing manual talks about the 'autothrottle' maintaining 'thrust'. I'm a by the book guy :D

Anyway, for the 737-300, Throttle Hold is at 80 kts (or 65 kts for models with older autothrottle computers.) Our procedure for aborts is to always disengage the A/T anyway regardless of the Hold function.

22nd Apr 2002, 15:15
I know about the throttle vs. thrust lever thing, but how come they're called 'autothrottle' and not 'autothrust'?;)

22nd Apr 2002, 20:13
Hmmmm.....this thing of the 'other pilot' keeping their hand at the base of the levers to follow up....bit dodgy.

The problem is if the pilot in charge of the thrust levers (the Captain? usually!) decides to abort the take-off.

If he's agressive in placing the T/L's to idle (as he should be) the other bloke better be quick to get his hand clear.

Before you jump all over me, try this yourself next time you're in the sim.

Put the start levers up, place your hand at base of the thrust levers (in a take off angle), now retard them to idle without removing your hand. See what I mean?

I'll bet it smarts.

Could be somewhat distracting to have a broken hand during the OGE actions!

23rd Apr 2002, 08:05
Idunno, you are actually correct in what you think.
If you are following the Boeing published procedures, then what you basically have are "areas of responsibility" with regards to the PF and PNF. Basically what you touch and what the other person touches. The throttle quadrant is the PF's area so, when thrust levers are advanced, PF would take his hands off and at the same time say 'set thrust' to the PNF, then PNF will have his hands there and say 'thrust set' and then hand the levers back to the PF. Well, that's just Boeing's way and I know not all airlines do that because everyone has and refines their own particular SOP. There is really no right or wrong, just different SOP.

Actually I've done it both ways, and even though you have your hands on the thrust levers and 'follow through' when thrust is advanced, you don't have to put your hands right at the base f the levers. If you follow up closer to the top (and it' easier to fine tune and set thrust at that position too) then the potential for any harm to yourself in case of an abort is minimal.

Semaphore Sam
24th Apr 2002, 23:08
As a rule, I hate 'rule-nazi's'. BUT...prior to V1, the only hands that belong close to the thrust levers (747-400, throttles for piston) are the hands of the person responsible for RTO decision-making (in our case PIC). No back-up before V1 by non-PIC, to prevent ambiguity & interference. If thrust is not set prior to 50 knots, it can be set easily by the PIC (manually); since this situation only occurs at very light weights, in 99.9% of cases it's not critical.

What I HAVE found to be critical is the 400' transition from TOGA mode to VNav; in certain conditions (ie; EEC malfunction with a poorly-written MEL) the thrust can reduce to idle; not very good at 394 tons in hot wx. It does get your attention; if, in addition, you were to experience an engine-out situation, your interest would increase further.