Landing distance available

[PEI_3721]

9.G re #37, do you have the Airbus reference; the 200 ft advice may be a hangover from the older VASI (PAPI/VASI) systems.
The TC AC does not indicate that PAPI is unreliable; indeed it is increasingly more accurate at lower altitudes due to the angular projection.
The AC covers the harmonisation of PAPI with the ILS, which shows that within given constraints – equipment spec / location, aircraft geometry, etc, the PAPI and ILS can be in agreement at the threshold.

Re #39, the reference to ‘Airbus’ Operational Landing Distances appear to be the relatively new and as yet not widely agreed view of ‘advisory’ landing distances. This does not appear to be the same as the term used in the VNV-Dalpa document.
“ No need to know all this crazy stuff.” There is an essential need to understand the basis of calculations (Go/No Go), irrespective of the data source, and to know the assumptions within those calculations.

[9.G]

PRO-SUP-34-00001989.0004001 / 17 MAR 11
Applicable to: ALL
Eye to wheel height on approach is 32 ft and minimum recommended wheel clearance over the threshold is 20 ft. Do not follow Precision Approach Path Indicator (PAPI) or “T”- Visual Approach Slope Indicator (TVASI) guidance below 200 ft when PAPI or TVASI Minimum Eye Height over Threshold (MEHT) is less than 52 ft. the last part has been added recently though, it seems.

[Microburst2002]

No. It has at least 8 years.

My old airline used EAG charts and MEHT was depicted in them, as well as the runway slope at the TDZ. I think that in that aspect, EAG is better than Jepp. The MEHT can be an important piece of info for some models. The slope awareness made me make better flares and landings.

I think that the land-within-60% rule allows for factors such as TCH. A 77 TCH means nearly 200 m extra and I find it quite excessive. As you say, LPC will account for every detail and that is good, but it still gives you a landing distance from 50', and it still stems from test pilot landings.

Personally I apply the 15% incrment rcommended by the FAA to assess the suitability of a runway when using the tables for a landing with abnormal configuration, when there is no requirement to land within 60%.

[donstim]

conclusion: use TORA as the LDA unless tere is displaced threshold.

This is incorrect. The LDA may be shorter than the TORA even without a displace threshhold if a portion of the runway needs to be used to satsify the runway safety area requirement. See, for example runway 09L at KATL (http://aeronav.faa.gov/pdfs/se_158_20SEP2012.pdf) where the TORA is 12390 and the ASDA is 11730.

[9.G]

well M2002, all depends on whether your airline has paid for it or not.
Following modification of performance module was made:

• Implementation of airlines’ requests
→ Possibility to consider additional line-up distances for misc. entry angles
→ Possibility to compute the go-around gradient requirement at a given height above terrain
→ Possibility to get glide slope and go-around gradient from airport data. As you can see it's available alas for cash.

[Microburst2002]

Dontsim

Yes you are right. I have learnt that thanks to you. In the Jepp, the LDA is specified for 9L, and a note explaining that some 200 m are not usable for LDA computation. And there is no displaced threshold. But the important thing is that every time you don't see an LDA in that field it means that you can use TORA as LDA. Otherwise use the specified value.

This thread was worth it, guys

Cheers!

[BBK]

Sorry guys

I still can't see why Jepps don't provide "threshold" LDAs for all runways. The situations where it's just the glideslope distance that is given is pretty useless since it does not relate to anything in the ops manual (perf section) or my company's QRH. I could add an approximate 1000 ft to the glide slope distance but I'd have a hard time justifying that on a line check!

Any thoughts? Appreciate all the background info which is interesting but it's what happens on a dark and dirty night with a double hydraulic failure on a wet runway that I'm really concerned about. As someone earlier mentioned I wouldn't be happy just to take the TORA as stated. If it is that simple then why don't Jepps say so?

[Citation2]

The best way to justify your LDA on the day of your line check or if you are simply looking for LDA information, go to your big Jeppesen binder, on Airport Directory part, you will find many pertinent informations such as LDA , and these are offical figures.

[9.G]

BKK, you're the master of your fate. If you need justification for your actions it's simple: lack of adequate regulatory guidance for landing performance calculation. I couldn't blame you for safest solution in particularly if you're RWY limited. The commercial department will only appreciate true costs of aviation in case of a disaster. All other times they'll be nagging at you neck and accuse you of being not resourceful enough...

[Microburst2002]

BBK

If the LDA from threshold field is blank, LDA is equal to TORA.
If it is not equal, Jepp gives it to you in that field.

[Denti]

Seems a lot of the confusion stems from jeps rather peculiar method of providing distances for the landing case. Other providers simply give the LDA for every runway.

[captakash]

Nice read.. But the question remains unanswered.
The question is not about a displaced threshold. It's about using the Landing Distance beyond threshold or the Landing Distance beyond Glideslope.
In my opinion, the landing distance beyond Glideslope is probably depicted for earlier or some country specific aircraft where the AFM or equivalent document have published figures for the ground run required from touch down to stop.
In case of Class A performance aircraft, the Landing Distance Required can only be compared to the Landing Distance Available. It is not dependent on the type of Approach.

The distance beyond Glideslope to me in a B777 seems to be of little use as there is no comparison from any manufacturer published value either in the AFM or Simplified Performance Charts.

Request any opinions on this view pls!

[westhawk]

The distance beyond Glideslope to me in a B777 seems to be of little use as there is no comparison from any manufacturer published value either in the AFM or Simplified Performance Charts.

I find the distance beyond G/S information useful as an awareness tool. The AFM landing distance data assumes a TCH of 50' and a G/S of 3 deg. The distance remaining after the G/S intercepts the runway surface would be approximately 1,000' less than than the declared landing distance available under those assumptions. (the G/S intercept would occur 1,000' beyond the threshold)

If I see a distance remaining after the G/S which is less than LDA minus 1,000', I consider it a warning that the AFM landing distance is optimistic for following the G/S to this runway. You might be using some of that 15 percent safety factor. This is a good time to make sure there is no extended flare if the LDR is very close to the LDA.

So together with the glideslope angle and the TCH, the runway remaining after the glideslope information can be useful in alerting one to a potentially surprising lack of runway remaining after touchdown. Especially nice to know when wind is variable and/or runway surface conditions are less than ideal.

I don't fly 777s, but that's not really important to the discussion. The same applies for any other transport category airplane with the same AFM landing distance assumptions. Airports like KMDW and KBUR have both had overrun accidents where an improved awareness of the situation may have been beneficial.

A 5,000' remaining after G/S note at a runway with an LDA of 6,500' would raise a red flag in mind if my AFM distance plus 15 percent safety factor was say 4,500'. Float for 3 seconds and it could be a little too close for comfort! With 6,500' minus 1,000, perhaps somewhat less so.