Go-around performance requirements??

[LOKE]

Go-around performance requirements??

Although Takeoff Performance has a specific FAR – 121.189, which specifies requirements for 121 carriers, Go-around requirements are a bit more vague. In fact some of the guideline documents – AC 120-OBS-11 & AC 120.29A, confuse rather than clarify requirements.

My background is in FARs and I am sure there are differences in JAROPS - undoubtedly more specific.

FAR 121 appears to have no specific requirement to ensure obstacle clearance during a go-around for each approach. In fact, regarding go-around, AC 120-OBS-11 states:

"(1) FAR parts 121 and 135 do not specifically require an obstacle clearance analysis for engine-out missed approaches or rejected landings. While it is not necessary to perform such an analysis for each flight, dispatch, or landing weight limitation, it is appropriate to provide information to the flight crews on the safest way to perform such a maneuver should it be required."

There is clearly a difference in practical, safety and regulatory concerns here - and I'm sure this thread will mention all.

I am interested primarily in FARs, but do not want to limit this discussion. I have learned that it doesn't do any good anyway.

Appreciate your comments,

LOKE

[safetypee]

I thought that the answer may be in a combination of TERPS and FAR-25. However, there appears to be a mismatch in the requirements for twin / three engine aircraft.

From TERPS:- No obstacle may penetrate an obstacle identification surface sloping with a 40 : 1 gradient (2.5 %). When climbing from MDA with the required gradient the aircraft shall clear all obstacles with the prescribed margins. (94 -164 ft ?)
PANS-OPS has a note:- When obstacles in the missed approach area determine OCA/H, a steeper gradient gives a lower OCA/H. This steeper gradient must be stated in the instrument approach chart. i.e. the operator is responsible for the a/c performance

FAR-25 -121 (d) Approach. In the approach configuration corresponding to the normal all-engines-operating procedure in which Vs for this configuration does not exceed 110 percent of the Vs for the related landing configuration, the steady gradient of climb may not be less than 2.1 percent for two-engine airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for four-engine airplanes, with--
(1) The critical engine inoperative, the remaining engines at the go-around power or thrust setting;
(2) The maximum landing weight; and
(3) A climb speed established in connection with normal landing procedures, but not exceeding 1.5 VS.

[None]

As you know, Missed approach criteria is published for each approach (missed approach required climb gradients and paths). If you are talking about a go-around, that may be different than a missed approach.

If you decide not to land and you are beyond the missed approach point (a rejected landing), the missed approach procedures may no longer be adequate. At this point you would have had to already brief yourself on any published obstacle departure procedures and be ready to execute those.

[Bally Heck]

Minima for any approach are based on OEI performance.

vizhttp://www.pprune.org/forums/showthread.php?s=&threadid=148947

[john_tullamarine]

One of the problems is regulatory/legal ... while the takeoff requirements can be prescribed with some confidence of legal testability and operational repeatability, the same cannot be said for the missed approach .....

I suggest that the question of obstacle clearance planning on the miss is a matter better left to operator risk management planning .. certainly, the pilot is in no position to do the sums .. which need to be done by ops engineers as the considerations are similar to takeoff OEI obstacle clearance.

[mutt]

as the considerations are similar to takeoff OEI obstacle clearance.

J_T, there is a lot of ambiguity in the FAR's, this is one of them. We are legally compelled to comply with the FAR25 requirements on arrival; we are not compelled to comply with the MAP gradients. Can’t say that I like the idea, but that’s straight from MrBoeing!

LOKE, IMHO an operator would be morally negligent not to provide crews with information pertaining to the actual airport Missed Approach Gradients. We limit the maximum landing weight to comply with the gradient.

Mutt.

[FullWings]

I brought up the SE GA scenario in the SE thread because I have met so many different opinions on the subject. The variation in replies would seem to confirm the general level of uncertainty in this area!

I (partially) remember why I brought this up: A long time ago I was operating into a medium-sized airfield in Portugal (could have been Spain?) and was idly considering the GA procedure. It all looked fine on one engine until you were clean, then you were left going up a valley with no real safe way out. I vaguely remember the published missed approach going out to some altitude on a radial then returning to the field. On one engine it looked like you would unable to turn back for some considerable time and then be so far up a valley there were almost no options left.

We had a bit of a think about what we might do in such a scenario (unlikely as it was.). In the end we thought it would be better to manoeuvre close to the airport, inside our circling radius, and depart in the direction of a more friendly missed approach for another runway.

It was a pretty academic exercise but it got me thinking about what was/wasn't checked/regulated in terms of SE missed approaches. I have to admit I'm still not sure now, even though I do a couple every six months in the sim. I think most training is too 'generic' to cover 'esoteric' points like this...

[BOAC]

If the airfield is a touch 'hairy' you SHOULD have an emergency turn or whatever you call it for departures? That is always worth bearing in mind for the unexpected.

[FullWings]

If the airfield is a touch 'hairy' you SHOULD have an emergency turn or whatever you call it for departures? That is always worth bearing in mind for the unexpected.Good point but you might be landing on a runway which has no departure or is not approved for takeoff by your Company...

[john_tullamarine]

Mutt,

I would take a VERY contrary view ..

(a) the FARs are MINIMUM standards and state so .. pretty typical for regs in other jurisdictions

(b) if an operator violates the declared regs then that is pretty silly

(c) but only marginally sillier than ignoring the duty of care type considerations to which I referred by implication ... just meeting the basic regs doesn't save the day in court ...

[BOAC]

Absolutely, FW, but it is always nice to know if and where ANY 'escape routes' exist!

[Empty Cruise]

Gentlemen,

we live with a conucopia of different certification procedures, 1 set for our aircraft certification (FAR25/JAR25), 1 for the procedures we fly (TERPS/Doc8168) and 1 for our airline operation (FAR/OPS1). These 3 sets of documents are by no means in complete alignment with eachother, but FAR/JAR25 is still regarded as sort of a baseline when designing the other sets of documents (no point in designing ops or procedures that no currently certified aircraft can fly :rolleyes: )

So, FAR/JAR25 must only be seen as a list of minimum performance and information requirements (along with a long list of other requirements that do not pertain to this discussion). See it as a checklist that the FAA/JAA use when they are ceritifying the aircraft ("Hmmmnn, must be able to... :yuk: Can it do that :confused: It can? Very good, checkmark, onto next item" :ok: ). It will not give you any specific data as to weather or not it is legal or safe to operate into or out of any particular aerodrome - only tell you what the aircraft as a minimum must be able to achieve, even when operating out of a MSL/ISA aerodrome with terrain as flat as a pool table for the next 100 miles around.

TERPS/8168 tell us how the procedures are designed and flown. But - at least Doc8168 - starts off by telling us that "These procedures assume all engines operative" :ouch: This means that we can in fact use tham as a kind of "poor mans" OEI performnace guideline. If your aircraft is able to meet the required climb gradient on the required track (both departure and MAP), then you can safely fly these tracks, adhering to your normal climb/speed schedule, as long as your net gradient does not fall below that required by the procedure.

Next, we look at FAR/OPS1. These documents also specify minimum performance requirements, e.g. ability to climb & maintain 1500 ft. above departure AD. This is not to say that on any given day at any given aerodrome this is a particularily sound or safe place to be (INN, CNF, FAE and other european pearls spring to mind), but you must comply with this requirement, even when departing an aerodrome in completely flat surroundings). In addition, FAR/OPS1 establishes rules for by how much you must clear obstacles laterally, vertically and what obstacles to take into account, both for the missed approach and for departure. When we look at theese rules, the specify much lower clearances and take far fewer obstacles into accoundt than e.g. Doc8168. Therefore, if you only use the 8168 missed approach/climb requirement, you may be facing quite severe TOM/LM limitations, whereas looking at the same obstacle scenario for either missed approach or departure using the FAR/OPS1 methology and clearances, you might find yourself not being mass limited at all. More mass = more fare paying mass = revenue = everybody happy (except of course the flightcrew who now have to comply with a 2-page emergency turn procedure :ouch: )

When comparing Doc8168 missed approach/departure and OPS1 requirements, you may find that you can fulfill the OPS requirements using the Doc8168 missed approach track. If this is not the case, an emergency turn procedure must be established, different from the missed approach/SID track.

:p Hope this helps - brgds,
Empty