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View Full Version : Why is 2000 fpm initial rate of climb on auto GA


Tee Emm
27th Dec 2013, 12:28
B737. On an auto go-around, pressing TOGA normally gives you a lower N1 than normal GA thrust since initial rate of climb is set at 2000 fpm.

However, on a manual throttle go-around it is normal to push the thrust levers to full GA thrust since the exact N1 to maintain an initial rate of climb of 2000fpm is not tabulated anywhere.

If it is considered "safe" to apply normal GA thrust in a manual GA, then why on an automatic GA with AT engaged, does Boeing used reduced power to maintain 2000 fpm rate of climb when full GA thrust is happily accepted for a manual GA?


After all, during a manual GA the PF opens up the thrust levers and says "Set GA thrust". And the PF does just that. He doesn't fiddle the books (thrust levers) to set 2000 fpm rate of climb.

PPRuNeUser0190
27th Dec 2013, 12:39
Hi Tee Emm,

From the FCTM:

"At typical landing weights, actual thrust required for a normal go-around is
usually considerably less than maximum go-around thrust. This provides a thrust
margin for windshear or other situations requiring maximum thrust. If full thrust
is desired after thrust for the nominal climb rate has been established, press
TO/GA a second time."

As for the thrust setting during a manual go-around. In our company we do not need to set maximum go-around thrust with both engines operating. Only a single engine go-around requires us to set maximum thrust. Maybe it's a company thing?

PPRuNe Towers
27th Dec 2013, 12:48
Makes me think about low capture altitudes, red and amber captions coming up due to available speed of stab trim versus ROC during an auto go around Tee Em.

obb

phiggsbroadband
27th Dec 2013, 14:10
Hi Tee Emm, Why would you require any more?... ATC has probably only cleared you to 3000ft anyway, to do a circuit and second attempt.

flyingchanges
27th Dec 2013, 15:19
Because climbing at 6,000 FPM is a bit much...

Capn Bloggs
27th Dec 2013, 22:04
Tee Emm, I suspect it's all to do with the difficulty of manually setting a lower than full power throttle setting. I don't fly the 737, but if as you say there are no 2000ft/min N1 figures anywhere, it's easier to just set full GA power and concentrate on flying the GA itself.

On two engines, it is obviously desirable to climb at reduced power and this is therefore designed into the automatics. Given that automatics are the preferred method of operation these days, Boeing assumes that they will be used on a GA and so have built in the 2000ft/min first press.

But FSF has now built-in a pay-wall to prevent easy access to the old ALAR Briefing Notes
Good one, FSF.

Icelandair Boeing 757-200 at Oslo Airport Gardermoen Norway 22 January 2002
Wow!

Hotel Charlie
27th Dec 2013, 22:26
With both autopilots engaged for an auto-land, the 737 starts trimming for the flare below 350-400' and with that trim setting and max GA thrust the autopilot would not be able to control the pitch me thinks :eek:
That's why :ok:

Matey
27th Dec 2013, 23:10
Next time you are in the simulator try closing your eyes and setting what you think is a reasonable go around thrust. On the 737-800 the relevant number would be about 88% N1 at a normal landing mass of around 63 tonnes. Keep practising until you develop the " muscle memory" for the correct N1. Then when you press TOGA, advance the thrust levers and call " Go Around Flap 15 Check Thrust" or whatever your SOP calls for the PM will only have to make minor adjustment if any to the N1 to achieve the desired performance.

BOAC
28th Dec 2013, 10:33
A common SOP on the 737 was to set full g/a thrust on a manual g/a but then you were permitted to reduce to ?not less than 90%? when the vs was upwards. Solved all the perceived problems.:ok:

sheppey
28th Dec 2013, 12:11
FCTM says: At typical landing weights, actual thrust required for a normal go-around is usually considerably less than maximum go-around thrust.


Boeing don't define "considerably less." Is that for instance, 10% N1 less than full GA thrust? Or, maybe 5%N1 less? Seems awfully vague which is possibly what the OP was getting at?


So what do you tell the PNF? How about: "Going Around - Set 10%N1 less than max GA thrust, please old chap and while you're fiddling with the thrust levers, you may as well give me Flap 15."

BOAC
28th Dec 2013, 12:34
See previous?

Denti
28th Dec 2013, 12:59
Boeing don't define "considerably less."

Well, Boeing doesn't define the N1 as that is demand scheduled and can actually reach full G/A thrust if required. It is scheduled to give between 1000 and 2000 fpm climb rate, with an aim to reach 1500 in an ideal case. That is availalbe whenever the AT system is active, for those airlines (like the one i'm working for) that use the ARM mode it is available in manual flight as well, thus precluding any requirement to figure out any thrust demand for oneself. However it ain't hard to do it manually if needed, just aim for around 1500fpm fly the aircraft.

aterpster
28th Dec 2013, 14:23
Denti:


However it ain't hard to do it manually if needed, just aim for around 1500fpm fly the aircraft.

That's easy for you to say. :)

BOAC
28th Dec 2013, 14:50
What is the problem with full power, g/a flap, gear up and then set 90%?

piratepete
28th Dec 2013, 15:12
I do lots of SIM and BASE training in a 767.I always brief the trainees to mimic the Automatics in both cases.Manually set approx. 1.25 EPR (Full EPR is 1.45).On a G/A reduce to this once you are CLIMBING.On a circuit, set this thrust once clear of the ground and say 2-300 feet aal.Works very well on any Jet, and keeps the handling "under control" makes the flying easier therefore SAFER.Ball-park numbers only.

PEI_3721
28th Dec 2013, 15:43
Re “… standards for the stable Go-Around.” A problem here is that Go-Arounds are rarely stable due to the dynamic and short duration of the event. A recent BEA study identifies many of the issues:- Study on Aeroplane State Awareness during Go-Around. (http://www.skybrary.aero/bookshelf/books/2404.pdf)
Also see the presentations from this conference (http://www.skybrary.aero/index.php/Portal:Go-Around_Safety) (first bullet).

The FSF’s ‘lock-down’ sets an appalling example for open safety and sharing information – the need for a learning culture; however most of the ALAR notes and presentations are available from SKYbrary - Flight Safety Foundation ALAR Toolkit (http://www.skybrary.aero/index.php/Flight_Safety_Foundation_ALAR_Toolkit)

stilton
29th Dec 2013, 08:58
Its a great piece of design and most welcome with a low altitude level off on a missed approach.

JammedStab
30th Dec 2013, 01:26
B737. On an auto go-around, pressing TOGA normally gives you a lower N1 than normal GA thrust since initial rate of climb is set at 2000 fpm.

However, on a manual throttle go-around it is normal to push the thrust levers to full GA thrust since the exact N1 to maintain an initial rate of climb of 2000fpm is not tabulated anywhere.



I have never flown the 737NG but with a single TOGA push for a go-around, do you not get the same target N1 setting display?

Is it old steam guage displays or a CRT screen for engine displays?

Natstrackalpha
17th Jan 2014, 16:52
Again, we have this subject, will no one (A320) heed my pleading call . . ?


(which is) Assume you are going around in an A320, at night, Temp+10 degrees Weight 62tons. and Select 190kts and keep F1, level at G/A altitude, stay Selected and drive yourself around the circuit/circle/procedure/to the hold/back on the approach/or atc/ whatever to put you back into the approach . . .slot - bringing the speed back to 180 when level since you have retained your F1 on the flaps.


Versus


Toga, still in Nav G/A - - - - where does this take you - whats your speed, where did that speed come from? I am sure there is an SOP for a G/A but in Automatic City, what is it? How many of you do the whole thing in Selected (whether manual or A/P)? Is it horses for courses, meaning - can Captain A do it his way and Captain B do it her way? - as both ways being equally effective and safe.

bubbers44
17th Jan 2014, 23:53
Other than in the sim I have never pushed TOGA because you scare the hell out of everybody for no reason. I just added climb power smoothly and did it manually. I know the new school is push a button and hang on.

Lord Spandex Masher
18th Jan 2014, 08:22
Why is climbing at 1500fpm scary?

rsbessa
18th Jan 2014, 12:59
One thing that I was taught during my initial training on the NG was the gouge: 400ft... "AT, LNAV, Autopilot, Set Radios for missed approach" . WORKS LIKE A CHARM!

So, this is the sequence I do nowadays: Toga (just once, as long as the situation doesn't demands a second push) , throttles forward, ask for flap 15 and after positive RoC is achieved, gear up. When the workload reduces to the chap next to me I ask him to Set Go Around thrust and, as soon as I'm above the amber altitude band, I call for the At, Roll mode and Autopilot!

After watching some GAs, there are a few things that I couldn't understand so far:

# Why most of the pilots forget that the AT is avaiable? Once this caused a huuuuuge flap limit exceedance to the operator Im flying. Something like 250kt with flaps 15...

# Whats the thing on pushing the damn toga button twice, even for low altitude level offs?

#Why some keep disconnecting the autopilot and the autothrottle to perform a go around? Don't they know that once you push the toga button the autopilot will automatically switch off (single channel GA)?

Just a few thoughts!

bubbers44
19th Jan 2014, 00:57
Automation just does what it is told. My check airman checking me out in the 767 wanted the leg from LAX to SAN one night and using automation ended up 300 feet high at 320 knots when I, the FO, told him to disconnect everything throttle way back and lower the nose when our clearance was 2500 ft. He had no idea how to fix the problem with automation he had screwed up. Hand flying sometimes makes things easy. First you have to know how to hand fly.

Natstrackalpha
19th Jan 2014, 20:59
Slightly, drifting off TOGA City, but,


my question is generally speaking - not necessarily in a go-around,


Whilst still in SRS.


1/. Can you move the t/l to CLB before accel alt . . ? What happens?


2/. What happens to the speed if you stop climb - when a/t armed and a/p in, whilst you are level? (Managed climb - but managed climb would not be managed if you stopped climb?)

safelife
19th Jan 2014, 21:58
You can, and arm CLB/OPEN CLB then, mean you'll perform the acceleration from then on.

OPEN DES
20th Jan 2014, 00:48
You can, and arm CLB/OPEN CLB then, mean you'll perform the acceleration from then on.

I am not sure what you mean.
Yes, you can prematurely select CLB thrust, but this will not affect the acceleration altitude. In fact it is routinely done in order to lower the climb rate whilst staying in SRS mode.

Once in SRS the only way to engage OP CLB/CLB mode is by:
-passing accel alt
Or
-pulling or pushing the ALT knob respectively.

The Thrust Levers do not interact with the vertical guidance modes, except for engaging SRS when TOGA is selected and Flap Lever -< 1.

2/. What happens to the speed if you stop climb - when a/t armed and a/p in, whilst you are level? (Managed climb - but managed climb would not be managed if you stopped climb?)

Not sure that I understand the question.

vilas
20th Jan 2014, 01:56
Natstrackalpha
1. In a GA, CLB mode (managed mode) is not available but only OPCLB.
2. SRS mode cannot have select speed. If approach was done in select speed it will automatically change to managed speed and in SRS if you change to select speed SRS will change to OPCLB.
3. THR RED and ACC altitude have different functions. Whenever you bring thrust levers to CLB, thrust changes to THRCLB and auto thrust to active ATHR from armed i.e. from blue. So now you have overspeed protection. SRS will continue till ACC ALT.
4. If you do not bring thrust levers to idle at THR RED altitude as long as you are climbing FMGS will restrict speed to VFE by increasing climb rate but it will no do so in ALT since ATHR is not active and you risk overspeed. Does it answer your question?

Icenor
20th Jan 2014, 02:18
That is availalbe whenever the AT system is active, for those airlines (like the one i'm working for) that use the ARM mode it is available in manual flight as well, thus precluding any requirement to figure out any thrust demand for oneself.

Doesn't AT disconnect when TOGA is pressed on single channel?

Denti
20th Jan 2014, 04:00
No. Autothrust remains active, but the autopilot will disconnect. However, in my outfit any ILS is flown dual channel until the AP is switched off.

Natstrackalpha
20th Jan 2014, 07:17
OPEN DES


A320


Climbing away, TOGA, SRS, Open, Managed - any climb you desire.


Suddenly - you decide to stop climb. If you use the v/s zero method, if this can done then what would happen to your speed?


1/.You would accelerate?
2/.The aircraft would level but the speed would default to the climbspeed what was?
3/. The aircraft would settle down (given time) to a temporary cruise speed for that WAT.


My question is we were climbing and we stopped climb. (as opposed to simply levelling off) by this I mean.


(These are unfair questions - I should be paying you money).

One more, question, if I may . . .

This is nuts, but I did not say it - about TOGA from an approach:


They said, (I forgot who it was now) they said that selecting toga when dual CATIII would have the aircraft in the same mode but in TOGA power therefore increasing speed in the landing configuration they slightly dramatized this configuration. So:


Approaching CAT III Dual say, one parameter lost and/or for some reason you decide to go-around - I am just verifying that simply setting TOGA will simply not cut it. Therefore,


Acceleration Alt pre-set pull or push ASSUMING IT IS ABOVE YOU.
set TOGA thrust. Result =.............and/but . . if you move the T/L significantly by pulling back say then the a/p will disc, and you can fly to your climbing attitude, attitude?


So - by pulling or pushing the g/a alt, thus having been pre-set - will not work as all alts are locked out during a catIII dual approach.


Confused? Don`t be. Here is a different hypothesis.


Approaching CATIII Dual. All is stable, then application of full back sidestick, a/p drops out, nose pitches up, if above 100 r/a then alpha floor toga, climb . . vfe, clean as you go.


Summary


1/. By stopping climb - what happens to the rest of it - spd, accel?
2/. In a cancelled CATIII App - apart from disc a/p set TOGA and fly it out
can a breakout (if that is the right word . . ?) be performed with the pb`s without touching the sidestick - I say no. But I am only learning,


(a mere husk of meaning)

vilas
20th Jan 2014, 07:36
Nats
I think you are confusing matters. Are you taking off or going round? I mentioned everything about GA in the earlier post. After takeoff you may be in CLB/OPCLB. If you now push to level SRS will change to V/S0 aircraft will accelerate and speed target will be initial climb speed 250. If thrust levers are brought to climb then speed protection is available otherwise you bust speed. What is the meaning of just levelling off? how doyou do that?

Natstrackalpha
20th Jan 2014, 08:06
"""What is the meaning of just levelling off? how do you do that? """


how do I do that? we are climbing, we want to level off, Lower the nose, select or keep airspeed, re-set . . . ? APT. re-set present alt - selected - becomes new cruise alt . . a/p in . . . . .


:mad: up haven`t I . .?!! (I think a month in a locked room with AUTOMATIC FLIGHT of the A320 is perhaps crucial here).


Thank you Vilas and Safelife and OPEN DESCENT.

vilas
20th Jan 2014, 15:29
Nats
If you lower nose to level out by not following the FDs which are in climb/OPCLB and thrust is in CLb then speed will increase till VFE/ VMO and then mode reversion will happen thereby FDs go off ATHR changes to speed mode, Managed speed reverts to select speed and is pulled back by thrust going idle.

Molokai
20th Jan 2014, 18:55
bubbers44 Automation just does what it is told. My check airman checking me out in the 767 wanted the leg from LAX to SAN one night and using automation ended up 300 feet high at 320 knots when I, the FO, told him to disconnect everything throttle way back and lower the nose when our clearance was 2500 ft. He had no idea how to fix the problem with automation he had screwed up. Hand flying sometimes makes things easy. First you have to know how to hand fly.


Was he Korean? Seemed he had difficulty in both automatics and manual flying.

Natstrackalpha
23rd Jan 2014, 07:51
Thanks vilas, Re: me posts above - I meant Thr Red when I asked about accel altitude. Sorry about the confusion.

(you guys know your stuff)