length of ILS approach

[captaincoldfront]

One for the planners.. What determins the length of an approach slope of an ILS approach?. Apart from the hieght above the ground from which it is started? I am looking in particular at EGLF, rwy 24 is 4.7d and 06 is 6d. I can sort of understand why 24 is short (proximity of LTMA to the east), but why is 06 longer ?

[B2N2]

I am not understanding your question.
Both approach plates show a final approach fix at 4.4 DME and both have a 3.5 degree glideslope which is a little steeper then the standard 3 degrees.

https://www.platinumairways.org/files/EGLFCharts.pdf

[Banana Joe]

I would assume you can find the answer to your question in Doc 8168 PANS-OPS.

[captaincoldfront]

Those charts are very interesting, but are 6 years old. Latest Jepps show 6 and 4.7d

[Field Required]

I would assume you can find the answer to your question in Doc 8168 PANS-OPS.

Rarely have I ever found a needle amongst that haystack.

[captaincoldfront]

Doc 8168 PANS-OPS simly states it can be between 3 and 10 miles for a 3 degree slope. IT does not say what determines the length of the final segment. EGLF is 3.5 degrees for both approaches.

[FlightDetent]

What about
Vol. II Construction of Visual and Instrument Flight Procedures
Section 4. Arrival and approach procedures
Chapter 4. Intermediate approach segment
4.2 Altitude/height selection

possibly
Chapter 5. Final approach segment

[FlightDetent]

The length of the intermediate approach segment shall not be ... less than 9.3 km (5.0 NM)

To fit a least the minimum I.A.S in tight airspace, obviously, the final segment might need to be shortened. OP suggested already,

More towards the question asked:
5.1.3 The final approach segment should be aligned with a runway whenever possible. All final approaches with a
FAF have an optimum length of 9.3 km (5 NM). The minimum final approach segment length shall not be less than 5.6 km (3.0 NM). This value also applies to the minimum distance from the FAF to the threshold except for non-RNAV procedures constrained by existing installations. Exceptions apply


Personally (EU roots, busy hubs) I found 7, or even 9 NM more convenient. Most probably that SOPs had been built around those. One idea left at the moment = noise footprint.

[swh]

Those charts are very interesting, but are 6 years old. Latest Jepps show 6 and 4.7d

My guess would be the MSA to the west is 2300 and to the east the control steps.

[B2N2]

Those charts are very interesting, but are 6 years old. Latest Jepps show 6 and 4.7d


:O
Sorry didn’t check the date lol.
I can only assume it has to do with an obstacle clearance requirement.
WAG.

[Red Four]

It looks to me that in this case it is for airspace containment purposes; the granted CTA's to EGLF would be as small as feasible, consistent with the purpose that the CAS is in place for in the first place. This reduces the impact on nearby aerodromes/aviation users.
The FAF being at the points where they are ensure that aircraft on the ILS will remain 500ft above the base of CAS of the various stepped down airspaces, whilst following the ILS profile down into the CTR.

Not obviously related to obstacles, as EGLF SMAC chart still has lower levels available (in theory), say if one was arriving/transitting IFR from outside CAS.

[chevvron]

It looks to me that in this case it is for airspace containment purposes; the granted CTA's to EGLF would be as small as feasible, consistent with the purpose for the CAS is in place in the first place. This reduces the impact on nearby aerodromes/aviation users.
The FAF being at the points where they are ensure that aircraft on the ILS will remain 500ft above the base of CAS of the various stepped down airspaces, whilst following the ILS profile down into the CTR.

Not obviously related to obstacles, as EGLF SMAC chart still has lower levels available (in theory), say if one was arriving/transitting IFR from outside CAS.
You also have to remember that aircraft must be vectored to enable them to establish and stabilise on the localiser a MINIMUM of 2nm before glidepath intercept and aircraft must be vectored not less than 2nm inside the boundary of CAS
I originally designed the Farnborough procedures to use alt 1,900ft as the 'platform' altitude but for some reason since I retired, the've been using a higher altitude; it was 2,400ft before CAS but what they use now I don't know.

[chevvron]

I am not understanding your question.
Both approach plates show a final approach fix at 4.4 DME and both have a 3.5 degree glideslope which is a little steeper then the standard 3 degrees.

https://www.platinumairways.org/files/EGLFCharts.pdf
That's because I designed the procedures for a platform altitude of 1,900ft and 4.4nm equals glidepath intercept at that altitude.
We could have dropped the 24 glidepath to 3 deg but the Airport Director and I (then a retired Air Commodore) decided that it was best not to as we had enough trouble with NIMBYs already; if they found out that aircraft were to pass 25ft or so lower over their homes, they would have been yelling for another public inquiry.
But don't let on; I didn't tell you that anyway.

[chevvron]

Those charts are very interesting, but are 6 years old. Latest Jepps show 6 and 4.7d
Jepp charts are immaterial; according to the UK Flight Safety Committee, they are not checked or regulated by an independent source, so the only definitive charts are those in the UK AIP.
The reason for the difference is that the platform altitude on runway 06 post CAS is alt 2,500ft whereas on 24 it's 2,000ft, the '6' and '4.7' representing glidepath intercept ranges.

[ShyTorque]

That's because I designed the procedures for a platform altitude of 1,900ft and 4.4nm equals glidepath intercept at that altitude.
We could have dropped the 24 glidepath to 3 deg but the Airport Director and I (then a retired Air Commodore) decided that it was best not to as we had enough trouble with NIMBYs already; if they found out that aircraft were to pass 25ft or so lower over their homes, they would have been yelling for another public inquiry.
But don't let on; I didn't tell you that anyway.

I always understood the steeper glidepath angle was to avoid "Cody's Tree".

[FlyingStone]

Jepp charts are immaterial; according to the UK Flight Safety Committee, they are not checked or regulated by an independent source, so the only definitive charts are those in the UK AIP.

How many operators or pilots use AIP charts in their flightdecks in lue of Jeppesen/LIDO/NavBlue?

[FlightDetent]

How many operators or pilots use AIP charts in their flightdecks in lue of Jeppesen/LIDO/NavBlue?True in real life. On the hair-splitting side: How many operators or pilots who use Jeppesen/LIDO/NavBlue charts in their flightdecks have read the small print on the Supplier's Disclaimer attachment to the sales contract?

As long as updated 3rd party package is a far fetch, and the AIP pages have all the information you'd need, it never hurts to drink from the source. It's free too.

[chevvron]

I always understood the steeper glidepath angle was to avoid "Cody's Tree".
Not since it was 'stolen' by DRA/DERA/Qinetiq and moved to Cody Site about a mile to the northwest.
3.5 deg GPs were adopted due to a design system called 'APATC-1' which was mandated for MOD airfields back in the '80s.
This involved a different way of calculating approach minima compared to the ICAO method used for civil airfelds, the 'dominant obsatcle' on runway 24 being --- the control tower!!
Once that was demolished in early 2003, we could have reduced to a 3 deg GP under both APATC-1 and ICAO methods of iap design.

[FlightDetent]

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1027x712/snippet_eglf_3f71cb61fc7488460a469ee06ea58d60bc034179.png

Recent. #gotitfromafriend

[FlyingStone]

True in real life. On the hair-splitting side: How many operators or pilots who use Jeppesen/LIDO/NavBlue charts in their flightdecks have read the small print on the Supplier's Disclaimer attachment to the sales contract?

As long as updated 3rd party package is a far fetch, and the AIP pages have all the information you'd need, it never hurts to drink from the source. It's free too.

All true. Apart from the actual operating minima, that is :)

[captaincoldfront]

'The reason for the difference is that the platform altitude on runway 06 post CAS is alt 2,500ft whereas on 24 it's 2,000ft, the '6' and '4.7' representing glidepath intercept ranges.'
You seem to be a man who knows what your talking about Chevron.. So why the diference in platform altitudes?. if you designed it at 1900' why the change to 2500'?

[chevvron]

They changed to 2,400ft intially just after I retired back in 2008; dunno why because the system we used before that was to vector the IFR inbound at 1,900ft and keep any transits at 2,400ft passing traffic information to both aircraft so you didn't then have to try to 'control' a VFR transit to enable you to descend the IFR inbound through it when it was on the ILS.
I can understand using 2,500ft on 06 now they have CAS in order to stay above Odiham traffic, but why 2000ft on 24 I don't know especially as the base of their CTA is 2,000ft just south of Fairoaks and they're supposed to keep IFR traffic at least 500ft above the base.

[ShyTorque]

Not since it was 'stolen' by DRA/DERA/Qinetiq and moved to Cody Site about a mile to the northwest.
3.5 deg GPs were adopted due to a design system called 'APATC-1' which was mandated for MOD airfields back in the '80s.
This involved a different way of calculating approach minima compared to the ICAO method used for civil airfelds, the 'dominant obsatcle' on runway 24 being --- the control tower!!
Once that was demolished in early 2003, we could have reduced to a 3 deg GP under both APATC-1 and ICAO methods of iap design.

Yes, I do remember “Apache one”. In the 1980s I was based at the military airfield about seven miles to the south west.

Its introduction resulted in a rethink and a lot of discussion about how we calculated our approach minima. The “En Route Supplement” contained a few anomalies, especially as the RAF flew instrument approaches on QFE. I remember ringing ATC at an airfield not far away to try to ascertain if the minima published in the “Red book” was calculated on QFE or QNH, because there was only a single figure stated, rather than the two quoted for other airfields. We were rather astonished to hear that the ATCO didn’t know!

[chevvron]

We didn't. We were told to refer to it a 'Procedure Minima' eg 'vectoring for PAR approach to runway 28, procedure minima is 'XXX', confirm decision height and intention'.
Some years later we did get 2 sets of minima when, with much fanfare, QNH based procedures were introduced. My boss and I attended a combined briefing for Odiham and Farnborugh ATC units at Odiham where the inimitable Dave Harrison from No 1 AIDU gave us a thorough rundown.
A couple of years later, after what was rumoured to be a cock up by an 'elderly gentleman' mistaking QFE for QNH, the procedures were switched back to QFE based with no 'publicity' although for some reason, Farnborough ATC didn't receive the 'change' to JSP318a where it was notified and we were not told by other means so were mystified when our aircrew suddenly started asking for QFE before departure!
NB: If you're wondering why I put 'a type of dog up' I didn't, that's what Pprune software has changed what I actually typed ('a c0ck up').