PDA

View Full Version : Racetrack procedure - when to descend


aviationbus
17th Aug 2015, 10:53
Hi guys, operational doubt on a ILS with racetrack:

http://s16.postimg.org/ij97t5w75/Racetrack.jpg (http://postimg.org/image/ij97t5w75/)

Cleared to DERUX, 5000ft, full procedure. When can I descend to 4000ft?
Some people say as soon as you reach the D14 point and turning inbound, some say when established with half scale deflection. Procedural experts are welcome.

Many Thanks

flapsupdown
17th Aug 2015, 11:05
When established on the inbound track (i.e. within half scale deflection)

Major Cleve Saville
17th Aug 2015, 11:15
I agree: When established on the inbound track (i.e. within half scale deflection). The 14 DME is published/quoted as part of the hold.

aviationbus
17th Aug 2015, 11:23
Thanks, this is what I thought and makes more sense to me as well but look at the planview on the LIDO plate...

http://s29.postimg.org/un4v3pzrn/Racetrack.jpg (http://postimg.org/image/un4v3pzrn/)

172_driver
17th Aug 2015, 11:28
If I read Jeppesen I would say 4000 when established on 013 inbound.
If I read LIDO I would say 4000 passing D14 and starting the turn inbound.

Again proves how ambiguous plates can be. I've always held Jeppesen in high regard for providing the least ambiguous charts.

aviationbus
17th Aug 2015, 11:36
...and this is the AIP plate.

http://s28.postimg.org/isctcez8p/Racetrack.jpg (http://postimg.org/image/isctcez8p/)

I would really like to hear the comments of a PANS-OPS procedure designer in this case.

cosmo kramer
17th Aug 2015, 15:32
According to the AIP plate horizontal view the descend starts at D14 IPE = LIDO is right.
*Note there is no 14NM inbound, so it has to be 14NM outbound on the downwind.

There are some dotted lines showing the STAR. It appears there is an approx. 16-17 nm arc. What is the minimum altitude for the arc, prior to D12 IPE?

vdbroeck.net
17th Aug 2015, 16:03
Major, where did you see a holding over DERUX ?
As soon as you reach the D14 point in the outbound of the RACE TRACK and turning inbound you can start your decent to 4000.

vilas
17th Aug 2015, 16:03
AIP vertical profile clearly shows that the turn from 14DME is level at 5000' and descent when 14 DME inbound.

Stone_cold
17th Aug 2015, 17:56
Aviation bus :

Extract from ICAO Doc 8168 Vol II
3.3.3 Flight Procedures for Racetrack and Reversal Procedures

3.3.3.4 Descent . The aircraft shall cross the fix or facility and fly outbound on the specified track descending as necessary to the specified altitude. If a further descent is specified after the inbound turn, this descent shall not be started until established on the inbound track (“established” is considered as being within half full scale deflection for the ILS and VOR, or within ±5° of the required bearing for the NDB).

I would suggest that the D14 is solely to define the dimensions of the Racetrack pattern ( DME vs time) and not as a descent point . Interpret as you wish .

RAT 5
17th Aug 2015, 22:36
What adds to the confusion is on the AIP chart, which IMHO is the source document for the commercial chart publishers, to shows a descending dotted line "from STARS" so as to be 4000' at 12DME. This routing is between the 14nm point and 12nm point and is depicted as almost a straight in. This would suggest a descent from 5000' at 14nm is safe. However, the Jeppesen chart shows 5000' - 4000' as being on 013 track. Could this be the interpretation of the chart publishers? LIDO shows a descending turn which seems safe according to AIP.
Next question: if in doubt ere on the side of caution. If you hold 5000' until inbound 013 can you descend to meet the profile? Yes.
I understand the question because of the confusion. Can you achieve the task required erring on the safe side? Yes. But is always gratifying to solve the puzzle. If you are an airline you should have a Nav/performance dept. They should have contact with the chart providers. Throw the question at them. The company has a duty of care to its crews not to endanger their operation. It would not be the first time an error has been discovered. Confusion is never healthy in our game.

cosmo kramer
17th Aug 2015, 23:32
Seems Stone_cold answered the question black on white. So my previous answer has to be wrong and the LIDO chart be in error.

Given that it's LIRZ, an Italian airport: no wonder there are possibilities for confusion. :oh:

Skyjob
18th Aug 2015, 01:15
I would interpret these charts as RAT5 did, hold 5000' until 14 DME before selecting a lower altitude of 4000' until 12 DME inbound on 013, then selecting 3400', etc...

However to FLY the approach I would use CDA technique, maintaining 5000' until G/S intercept once LCO established. Code the FMC with ABOVE altitudes to facilitate this and MONITOR the aircraft performance.

Simple :)

Oakape
18th Aug 2015, 02:28
You must maintain 5000' while in the hold, unless there is a specific clearance (charted or by ATC) to descend in the hold. There is no charted descent below 5000' in the hold in this case. Therefore, further descent cannot be commenced until you are established on the ILS approach & cleared for that approach. To be established on the ILS you must be within 1/2 scale deflection on the normal localizer (not the expanded scale).

The dotted lines shown that relate to the STARs are irrelevant to the question. They are tracks to the D12 IPE position on the localizer & will have their own descent instructions to get you to 4000' by that point.

The D14 IPE position is solely to define the holding pattern outbound leg & is not a descent position, as seemingly incorrectly shown on the LIDO chart. There is no timing for the outbound leg of the pattern in this case.

The LIDO chart is interesting, in that the vertical profile doesn't show the holding pattern, as the other two do. And it has the approach commencing at 4000' rather than 5000' on the other two charts. It appears that the descent in the hold to 4000' as shown on the plan diagram is to link the hold with the approach. Perhaps they have permission from the approach designer for that descent. The descent steps on the STARs may give a better picture of the terrain & associated safe altitudes in that area, given that they take you to 4000' at D12 IPE for the commencement of the approach, as depicted on the AIP chart.

There has always been difficulty showing holding patterns on the vertical profile portion of the approach chart. The inbound leg, outbound leg, inbound turn & outbound turn are all shown as a single horizontal line. In this case, on the AIP chart, the outbound turn is shown as a horizontal line to the right of DERUX & the inbound turn as a horizontal line to the left of D14 IPE. You will notice that the descent commences at D14 IPE, tracking to the right. As these charts a drawn for the nil wind case (the pilot allows for wind on the day), the inbound turn will be complete at the same point that it started - approximately D14 IPE (allowing for slant range differences). Therefore, you would expect a descent commenced at the completion of the inbound turn to be shown at approximately D14 IPE, as it is. If the descent was to be commenced during the outbound turn, it would be depicted going to the left as far as the horizontal line does & then back to the right, as the inbound turn is wholly depicted by the horizontal line to the left of the D14 IPE point.

The Jepp chart depicts the descent commencing before D14 IPE, but the line is drawn to the right only, so descent could only arguably commence from a point in the inbound turn where the aircraft is moving back towards DERUX, which be at least half way around the turn.

A track reversal & altitude change during the turn on the vertical profile section of the chart is neatly depicted in the missed approach climbing turn shown on the AIP chart.

Major Cleve Saville
18th Aug 2015, 03:30
vdbroeck

Major, where did you see a holding over DERUX

Er.....that would be the HP DERUX. You must be ex-Sabena.

Racetrack procedure.
A procedure designed to enable the aircraft to reduce altitude during the initiai approach segment and/or establish the aircraft inbound when the entry into a reversal procedure is not practical.

Looking at the AIP chart I don't believe this was ever intended to be a racetrack as such as as there seems to be no descent outbound in the Hold/'Racetrack' shown. I believe if the national authority had intended a descent after 14 DME in the turn it would have been shown in the vertical profile.

The fact that on the AIP chart there is a thin line for the hold/racetrack makes me think it is a hold and not part of the IAP.

Personally I am not a big fan of Jeppesen charts, to me these days too many errors and misinterpretations ambiguities and too slow a revision process. Also lacking clarity. Designed with Lawyers not Pilots in mind?

Airmanship says even if you descend in the turn you are not going to have a problem anyway, but with 8 miles to loose 2200' I think I would wait until established inbound

peekay4
18th Aug 2015, 04:35
However to FLY the approach I would use CDA technique, maintaining 5000' until G/S intercept once LCO established. Code the FMC with ABOVE altitudes to facilitate this and MONITOR the aircraft performance.
That's probably fine for this and most other approaches (plus great for noise abatement) -- but I wouldn't say this is best practice either.

- Depending on where you complete the turn, staying at 5000 ft means you may be intercepting the G/S from above, which is not ideal

- It also means joining the G/S far away from the designed intercept point, e.g., in this case maybe around 12nm out instead at the 6nm FAF. Many glideslopes may not be reliable past 10nm, and by the time you do get a G/S lock at 10nm you'd have to dive down to intercept had you stayed at 5000 ft.

(On a typical ILS setup, the UHF glideslope signal normally has a much shorter range than the VHF localizer signal).

The ICAO recommendation is still to intercept ILS from below, hence the LIRZ procedure above is designed the way it is, with a step down to 2820 for a normal G/S intercept.

In the GPS/GBAS world there will be more freedom to design and fly approaches more efficiently.

aviationbus
18th Aug 2015, 13:29
Many thanks for your replies.

cosmo kramer
18th Aug 2015, 13:36
Back to the LIDO chart, it is actually correct as well, only we are interpreting it wrong.

From the legends and table part of the LIDO general section, it is clear that the 4000 feet written during the turn is just the way LIDO depicts Initial Approach Altitude, and that is doesn't refer to the D14 IPE.

That the descent can't be initiated until 1/2 deflection, LIDO assumes that we as pilots would know. For the racetrack, there is a note in legends and tables that refers to rules and regulation, with the same text Stone_cold quoted.

So both charts are correct.

Oakape
18th Aug 2015, 21:32
Thanks cosmo kramer. I would imagine that if you were using LIDO charts in your day to day operation, you would be used to that. I guess it only becomes confusing when you normally use one of the other charts. That being said, I used to use LIDO charts 3 or 4 years ago & still didn't know that. It never hurts to get into the legends & tables section periodically.

Feather44
20th Aug 2015, 18:04
If I read Jeppesen I would say 4000 when established on 013 inbound.
If I read LIDO I would say 4000 passing D14 and starting the turn inbound

I tend to agree with that

aterpster
21st Aug 2015, 21:44
The moral to this story: Use only the charts that you really understand.