Autopilot - TOGA switch

[Calapine]

Quoted from http://www.skybrary.aero/index.php/Autoland:

The approach can always be discontinued at any time by pressing the TOGA (http://www.skybrary.aero/index.php/Take-off_/_Go-around_%28TO/GA%29_Mode) switches or in the case of an Airbus, by advancing the thrust levers to TOGA detent. Depending on the aircraft type or autopilot system installed, the auto pilot may or may not disconnect at this point. Most aircraft capable of an autoland also have the capability of performing a go-around with the autopilot engaged.My question would be what exactly happens on activing TOGA-switch/TOGA detent thrust with AP activated.

Does the autopilot perform a generic TOGA-reaction such as "TOGA thrust, nose up" or is actually a complex maneuver/flightpath that is different for every airport?

I am assuming there is a pre-defined flight corridor pilots have to follow if they abort a landing for any reason, is that correct?

Thanks in advance. :)

[HEATHROW DIRECTOR]

In response to your last question, yes, there are laid down procedures which to be flown in the event of a go-around. However, at busy airfields ATC will often issue instructions to re-position a go-around back into the traffic pattern.

[suninmyeyes]

Calapine


On a modern Boeing pressing the TOGA switch will result in a pitch up to approximately 15 degrees and thrust being applied which will give a climb rate of 2000 feet per minute. A second press of the TOGA switches will give a full power climb.


The flaps will have to be brought into 20 degrees and then the gear can be raised once the aircraft is climbing. At acceleration altitude which is usually 1000 feet above the airfield the target speed has to be manually increased and the nose will then automatically lower.


When it comes to the navigation part, yes as Heathrow Director says this differs at different airports and even different runways at the same airport. Take for example Heathrow 27L and 27R. One now has a missed approach level off altitude of 2000 feet and the other has 3000 feet. On one you maintain runway heading to level off altitude, on the other you do not. To navigate laterally in the missed approach at a height of 400 feet the LNAV button is pushed and provided the correct runway had been programmed in for the approach the aircraft will fly the correct lateral profile for that missed approach. However it is normally after LNAV has been pushed that ATC then give an amended missed approach clearance involving a heading and climb altitude. If the automatics and altitude selector and FMC are correctly used the aircraft will level off at the correct altitude. If something is missed it may level off high or low.


So a missed approach is not fully automatic and lots of human intervention is necessary. It is a high workload situation when not expected and frequently something is omitted. I watched a 747 at LHR a few month ago do a missed approach, probably due to the landing aircraft in front failing to vacate the runway in time. I watched it climb away to a least 2500 feet with its gear down before it went into cloud. I suspect this was because the non handling pilot never called "positive rate" which is the prompt to raise the gear.

[Tom!]

To add to the excellent post above:

On the 737 it depends what happens. If you had both autopilots engaged for an automatic landing the aircraft will also fly an automatic go-around in TO/GA mode (15° pitch up, AT sets reduced GA thrust etc...). Gear and flaps are always retracted manually.

Press the TOGA switch on a single autopilot approach and the autopilot will disengage and you will have to fly a manual go-around. If the autothrottle was still engaged it will still increase thrust to reduced GA for a single press. If autothrottle was disengaged as well (manual approach) the only thing pressing TO/GA will do is make the flight director symbols on the screen point up, rest is up to the pilot.

And in both cases at 400ft above the ground we select the direction we want to fly depending on the airport. Either using the plan in the navigation computer or just flying a heading.

[Denti]

And even the navigation part depends of course on type and customer options. On our 737s LNAV will automatically engage above 50ft, speed bugs will automatically increase during acceleration, so nothing needs to be done except pulling up the gear and flaps.

On the airbus setting the thrust levers to the TOGA detend will do the same as the TOGA buttons on the boeing, except that it gives full go around thrust as well, so if you have a lower level off altitude push it into TOGA and then pull it back into the CLB detend to get a lower climb thrust. Navigation will follow the missed approach path except if a HDG or TRK is already preset.

[Tom!]

Ours just follow the ground track you had U ntil you press LNAV or HDGSEL. so many options.:}

[Denti]

Yup, boeing is probably the only company that offers a product with a bigger option catalogue than porsche.

Apparently the TO/GA to LNAV feature is one of those. The downside is that in a single engine automatic go around it will automatically kick off the rudder pretty rudely when LNAV engages.

[Tom!]

Would not be a problem for us, no rudder servo option (so only cat3a as well)

[Calapine]

Thank you for the replies everyone. That clears it up somewhat. :)

[Oilhead]

Calapine


On a modern Boeing pressing the TOGA switch will result in a pitch up to approximately 15 degrees and thrust being applied which will give a climb rate of 2000 feet per minute. A second press of the TOGA switches will give a full power climb.


.

Can you give me a formal reference for that statement? I have always believed your statement to be exactly correct, but I cannot find any reference to the dual TOGA go around double push difference. I fly the 752, 753, 764, 763, and I cannot find any reference to the first push, second push difference. Thanks!