IFR Transits below sector safe altitude query.

[engineoff]

Whilst flying earlier today and requesting an IFR transit through Class D airspace at 3000' , I was politely informed that to do this required a climb to the sector safe altitude which in this case was 3400. I was however complying with IFR rules for my planned track ie. 1000ft clearance within 5nm of track. Providing this is maintained then surely SSA (whilst giving a greater seperation safety buffer) is not required? (In the circumstances a climb was not preferential due to the awful British weather!) Will controllers generally refuse to offer IFR transits below SSA or will as I have heard in the past simply be informed that I am responsible for my own seperation from terrain?

[Chilli Monster]

Controllers will not descend you below SSA if inbound, or will not give an initial level below SSA if outbound.

As an en-rte transit however you are responsible for determining if you are complying with the Instrument Flight Rules - in this case, as you say, the 1000ft above any obstacle within 5 miles of track. As such you cannot be denied a transit for the reasons you describe above (Any other reason - maybe, but not this one).

If the route was transitting Class 'D' then it sounds like the controller concerned needs a refresher lesson in a) local topography and b) Rule 29.

[ILS 119.5]

2 Questions. Whose airspace did you wish to transit? and What service did you require outside?

[engineoff]

Handed over from Newcastle to Teeside after transitting initially out of the Newcastle CTR VFR at 3000'. Due to more solid weather further South I would have been unable to maintain VFR at 3000, and on queried over VFR and IFR elected to continue IFR. I was then informed of SSA of '3400' (I think off the top of my head?) and that I would then require a quadrantal of FL45 or 65.... In the circumstances with the 55kt headwind already , I decided to descend and continue VFR, which with the clearing weather proved to be no problem.


RIS requested although with the lower levels tend to be offered a FIS.

[ILS 119.5]

When entering Class D airspace you automatically receive a Radar Control Service therefoe under this controllers are not allowed to have IFR aircraft below. They could use the "keyhole rule" if they wanted. Outside CAS a RAS will only be provided in most cases at terrain safe levels and a RIS can be below.

[Voroff]

I think passing the qnh, ssa/msa and instructing the pilot to maintain own terrain clearance is sufficent. Howeverer I will look it up as i've never worked in class D airspace.

[spekesoftly]

When entering Class D airspace you automatically receive a Radar Control Service ........

Bit of a sweeping statement, the clearance could be procedural.


Wrt Terrain Clearance - see MATS Part 1 Section 3 Chapter 1 Page 5 para 9.1.1

Which basically says that if a pilot is flying at, or has requested, a level below MSA and can accept an ATC clearance at that lower level, then a reminder of the highest sector altitude should be issued.

It does not say that such clearances should be refused.

However, some MATS Part 2 (local ATC unit instructions), may specify minimum levels for the provision of a particular ATC service.

[This is a crisis]

Quite agree speaksoftly.

We have a similar situation in that beacuse a hill just slightly infringes out CTA (by about 1 mile!) we have a higher SSA in that quadrant. People regularly transit at 3000' and get a reminder of the SSA.

[FWA NATCA]

Engineoff,

As a controller I can't vector an IFR aircraft below my minimum vectoring altitude. The minimum vectoring altitude is derived from surveys of obstacles, and it seems often by noise sensitive zones.

The only exception is during an emergency, but even here the controller must be extremely careful because we live in a society where suing everyone for anything prevails.

Mike

[spekesoftly]

Mike,

Agreed, but we must draw a distinction here between the minimum levels applicable to vectoring an IFR aircraft within a defined Radar Vectoring Area (RVA), and the MSA, which is usually higher because it is based on obstacles within a bigger area.

[engineoff]

FWA Natca,

Thanks for that. Is minimum vectoring altitude the same as sector safe (presumably never lower) ?

ILS 119.5

Any chance of a brief description of the 'keyhole' rule you mentioned . preferably in simple enough terms for a pilot to understand?!

[spekesoftly]

engineoff,

If you go to this (http://www.caa.co.uk/docs/33/CAP709.pdf) link, and then look at Appendix A (Examples of completed RVA charts), you will see that the minimum altitude to the S/W of Teeside within the RVA is 1800', but that the MSA (within 25nm of the ARP) is 3400'.

[engineoff]

spekesoftly: Thanks for the link ; all making sense now! Did note that the TA at Teeside is 6000 ft so my next question is how can I have been suggested to climb to FL45 which incidentally was also non quadrantal for the track?

[keithl]

Will someone please define SSA for me? I've been making a study of all these different MSA terms and it seems to me that there is a lot of confusion. SSA doesn't exist in PANSOPS.
I believe you are referring to the MSA within a particular sector of the 25nm MSA circle - confirm?

[DFC]

A very important note:

The requirement to be 1000ft above all obstacles within 5nm under IFR is measured from the aircraft. It will only be measured from track when the chosen form of navigation can keep the aircraft exactly on track 100% of the time and as we all know, not even visual navigation can guarantee this accuracy.

Thus, IFR flights will normally be 1000ft above all obstacles within 10nm or more from track to allow for normal navigational inaccuracies.

I seem to remember from somewhere that when a pilot requested change from VFR to IFR, that pilot was to be reminded of the appropriate safe altitude if the flight was below that level. Makes good sense also!

Unless the aircraft was being radar vectored, the pilot would be responsible for terrain separation and within 25nm of the reference point, the information available to the controller is the Sector Safe Altitude. Thus IMHO, this would be the most appropriate information to provide.

As for appropriate Flight Level. Perhaps this question displays the problem with altimeter setting in the UK.....the myriad of transition altitudes. However, the rule is clear in that it applies to aircraft operating above 3000ft AMSL or the transition altitude which ever is higher. Consequently, this pilot culd have legally cruised at 3400ft QNH during the transit.

However, that leads me on to.......to what distance from an aerodrome or holding fix does the local transition altitude apply?

Personally, I use 25nm as a guide but does anyone have a definitive figure?

Regards,

DFC

[letMfly]

Depends where you are DFC. At my Unit the "local" transition altitude is only used within the CTR.

Getting back to the original question, IFR aircraft flying within controlled airspace for which a RVA (radar vectoring area) chart has been published can't be allocated levels below those given on the chart unless the aircraft is inbound and on a closing heading for the relevant approach aid (MATS Pt1). SRG specifically banned the use of the radar "keyhole" within RVAs several years ago. The only way around it is if a pilot is flying in VMC and elects to provide his own terrain clearance, but even this is open to debate!

The above applies to the UK only as far as I am aware.

letMfly

[brimstone]

DFC - as letMfly indicates, where an aerodrome lies within a Control Zone the Transition Altitude for that aerodrome is applicable only within its Control Zone.

Elsewhere in the UK the TA is 3000ft.

engineoff - as you cleared the Newcastle CTR the Transition Altitude would have changed to 3000ft, therefore reference to quadrantal flight levels would have been appropriate.

On transiting the Teesside CTR where the TA is 6000ft you would be cleared through at an altitude on their QNH.

[ILS 119.5]

I didn't realise that SRG had banned the use of the keyhole rule, but to answer one of the members questions the keyhole rule stated that an a/c cannot be below 1000' above the highest fixed obstacle within 5nm of the a/c and 10nm ahead of the a/c 15 degrees either side of the a/c's track. This is reduced where a RVA has been produced for the area/airport. I think the figures are right but it was something like that. If SRG has banned the use then it should not be in the CAA MATS Pt 1 but I'll try and check.

[letMfly]

ILS 119.5

Sorry if I've confused you, but the keyhole can still be used - only not within RVAs.

letMfly

[DFC]

This point raises a further related question;

The MSA applies out to 25nm from the beacon.

Most Approach Radar Units operate out to 30nm or more.

As has been said above and from DOC 4444, the local TA only applies within the CTA/TMA/Vicinity of the Aerodrome.

Returning back to the original situation, if the pilot had been say 30nm from the airfield, what would the ATCO have told him/her the safety altitude or minimum safe level was and is this information available locally?

Regards,

DFC

[Voroff]

Well away from airports you have minimum safe altitudes governed by the regional pressure settings and the highest point in that pressure setting region. I think the Portree regional pressure setting region has the highest as it includes Ben Nevis.