GPS Letdowns

[MightyGem]

Colleagues of mine who operate out of a small airfield near London, are concerned about the number of occasions that they have witnessed civilian operators, both private and public transport categories, in breach of rules concerning flight at night / IMC letdowns / operations in reduced visibility & cloud base.

The most recent example was witnessed after a daylight landing at an airfield with a cloud base of 300ft AGL and 3000m vis. While walking from the pad a twin squirrel conducted a GPS? let down breaking cloud at 300ft & 90 degrees displaced to the runway orientation. (Airfield has no IFR / IMC let down)

Appropriate action in the past has ranged from discussions with the pilot, CHIRP reports, AIRPROX reports and information passed to the CAA.

However concern is growing that this is a widespread practice within the commercial world, due to the commercial pressure to complete the task. Since there is chance of a mid air with other aircraft and one of these flights, they are keen to receive feedback on how widespread this is over the UK?

Also does anyone have specific examples of TCAS assisting in exactly these circumstances?

PS: yes they are allowed to fly with 300' cloudbase.

[SASless]

TCAS....who the heck has TCAS....very few commercial operators will have that gear...why dear chap...that costs money and who will pay for it?

[ShyTorque]

SASless, we have TCAS, as do an increasing number of UK operators.

TCAS is a great help but it is only a part of the situational awareness equation. A radar info service is another part, as is listening to and speaking on the radio on the appropriate frequency. But you know all that already, MG.

Best not to cast aspertions before knowing the facts, so I won't comment on a particular case. However, I don't agree with people carrying out ad-hoc GPS letdowns per se, if for no other reason that the CAA doesn't allow it. Is it possible that some of these aircraft are being flown on VOR / DME / ADF letdowns that you are unfamiliar with?

[MightyGem]

The airfield in question does not have any published instrument approach procedures.

[SASless]

If the airfield has no IFR approaches...then the probability of more than one aircraft doing a GPS cloud break procedure seems very minor. Also, if monitoring the local radio frequency....then traffic separation can be done exactly like in VFR conditions.....but correct me if I am wrong...there would be no airplanes operating in 300' ceilings (assuming no IF approaches authorized) so traffic should not be that big a problem. If you are equipped with TCAS...that assumes the other aircraft must have at least a functioning mode C or altitude reporting ability for your TCAS to function. Now if the twin squirrel arrived offset to the runway....as described...was he not remaining clear of fixed wing traffic as required by the daunting CAA regulations? I might also ask you what in flight visibility and cloud base was as observed from the cockpit of the helicopter in question? Might it not have been sufficient for the pilot to have complied with all the restrictions placed upon him by the CAA? Did you perhaps have a chat with him over a cuppa and find out his side of the matter? I dare say....300' and 2 miles vis is not all that bad for a helicopter....that is better than my cross country VFR minimums....same cloud height but if as you stated....3000m vis...then six times my minimum vis requirement by Ops Man.

Just some thoughts on this.....at least you have GPS now....after all for so long those on the eastern side of the saltwater divide were loathe to acknowledge its existence....after all it is a US DOD thingy, you know ol' chap! Just wouldn't do to use such a device....why it just isn't the done thing you know!

Heheheheh! My , how things do change?

[Red Wine]

Oh..you have baited the hook yet again..........

Now see what swims by.........!!!

[MightyGem]

SASLess, we all know that in the land of the free there is a little more leeway in the these matters, for better or for worse. However, I'm not after the views of people like yourself, I'm more interested in the comments of UK operators, especially those that carry out what are, in this country anyway, illegal operations.

The crew that raised the point are not equipped with TCAS, so the first that they might be aware of another aircraft is when it looms out of the cloud directly in front of them.

Legalities aside, this is basically a Flight Safety problem. Is it sensible to carry out a blind approach when you cannot be 100% sure of where you are, and with probably no idea of what's going to be infront of you when you break cloud.

Flight Safety is no accident.

[ShyTorque]

MG,

I don't think you'll be getting any comments from those that "carry out.......illegal operations".

Do you? :D

[SASless]

Oh but Gem....that is the UK Ops Man ceiling and vis numbers I quoted you.....not the American one. Being the proud holder of a UK ATPL with IF rating , qualifies me for participation in this forum even if my several other ones do not in your expectation. Unless I really missed something....each of the questions I posed was offered to stimulate an elaboration of the situation so that we could better understand your concerns.

Do I understand you to say there are crews operating without TCAS in the area....thought it was common kit nowadays?

Gem....A previous thread started by one of our colleagues in Oz discussed the merits of GPS based point in space approaches and the consensus seemed to validate those procedures. A search might prove to be helpful in your consideration of these matters. I dare say, GPS provides very accurate postion locating.....much better than either VOR or NDB approaches....and except for glideslope.....probably just as accurate as ILS procedures. The "not knowing" where you are comment needs some discussion I believe......and most very definitely beats the heck out of Decca.

[OldBill]

I know of a couple of operators who use FMS approaches, one i believe has submitted the approach to the CAA. Some of the FOI also fly public transport for the same operator to remain current. So i presume it is being asessed by the CAA.
I hope we eventually catch up with the US on the approval of GPS appraches. If done properly with a FMS I personally think they are much more accurate than for instance a NDB approach. ;)

[Steve76]

Making your own GPS letdown is an easy way to an early grave. Better make sure your life insurance is paid up.

[Thomas coupling]

Didn't an S76 fly into a hill side in Ireland about 3 to 4 years ago doing this very same thing. 3 killed.

[GLSNightPilot]

Mighty Gem, a couple of points to ponder:

1. Flying at 300' ceiling, which you admit is legal, can give the appearance of coming out of the clouds, since the ceiling is often ragged, & the aircraft may have been hidden by a cloud hanging down, & you just couldn't see it coming until it flew below it, although it was never in the clouds. I wasn't there, I don't know what happened, but I have seen this exact scenario played out many times.

2. I have absolutely no knowledge of UK regs, but in the US, just because there is no public instrument approach that doesn't mean there is none at all. We fly many approaches using approach plates approved for a specific company or companies, requiring specific approval & training, & these are not available to the general flying public. They have been flown, tested, & approved by the FAA, but are not public approaches. Could this ever be the case in the UK?

[The Nr Fairy]

TC :

Your memory serves you right. Check Irish AAIU web site (http://www.irlgov.ie/tec/aaiu/1998Reports/1998-008/1998-008.htm) for further details. Total experience on board something in the order of 26000 hours between the three of them.

[Arm out the window]

You would have to be a ******** to make up your own GPS approach and descend to 300 AGL on the strength of it, because of the likelihood that:

a. it's not designed to stringent planning criteria and therefore probably not giving you the protection that an approach designed by professionals would do; and

b. seeing as no other bastard would know about it and you're probably keeping it hush-hush because it's illegal, you're likely to plough into someone else as you break cloud at the bottom of it.

[SASless]

Just read the Irish accident report.....to state it was the "homemade approach procedure" that caused the accident fails to accurately describe the situation. The PF was a stranger to the aircraft, operation, and area. The PNF was not instrument rated and had failed a previous IF Rating Checkride. They had not obtained a current weather briefing for the destination....and it is painfully apparant that Crew Coordination was very lacking. Imagine yourself as the visiting pilot.....running pickup....expecting to be a passenger....no weather brief....no crew brief....strange aircraft.....Boss sitting in the back.....imagine the stress he was under.

No accident can be attributed to a single cause.....it requires a chain of events to cause an accident.

I can see about a dozen links in this chain......the final result is three dead men.

Compare this to the Air Methods Bell 412 crash in Bluefield, West Virginia back in 1995 (or so) and you will see some interesting similarities and the 412 crew were on an ILS approach and hit a mountain 6.5 nm's beyond the airport while thinking they were on the approach side. That crash killed two pilots and two passengers. They were in a strange aircraft, were flying the spare that had been brought in that morning by the company check airman. They had declined the flight earlier because of bad weather, swapped over the equipment from the regular aircraft to the spare. They were now confronted with refusing an IFR flight in front of the check airman who was there to do IF base checks for a company that marketed IFR services and used that to set themselves above the competition. The PF was the Base Manager, Base Training Pilot, and Base Safety Pilot.

It isn't the approach procedure being flown as much as how the approach procedure is being flown that matters. Our Aussie friends are flying point in space GPS approaches and seem to be doing it quite safely. Several EMS operations in the USA are doing the same thing and are doing it quite safely. We have embraced GPS here in the USA and have approved approaches almost everywhere there is a non-precision VOR or NDB approach. It works here and Oz.....should work in Blighty.

Doing them without the proper authorization and flying IMC in violation of the rules is patently unsafe .....because of the traffic separation and ATC issues. Ask any Gulf of Mexico pilot.....how many times they popped out of cloud, rain, or some other block to vision, to almost run over someone else scud running!

[Nick Lappos]

I understand that the CAA is very reluctant to approve new or different approach procedures, mostly because it is hard work to them to change things, and also exposes one to risk of getting it wrong.

There is a lesson here, and as one of those Colonial malcontents, let me state it bluntly. The CAA does not actually own the sky, and if they don't approve procedures, that does not mean the procedures are not needed, and it does not mean the procedures will not be flown.

Basic needs must be met by Government, or Government will be left behind. There are hundreds of GPS approaches in the states, and thousands more coming. It has taken too long here, but things are moving. GPS approaches work, they are safe, accurate and ubiquitous.

If Government had invented email, we'd be putting stamps on our computer monitors! The progress in medical procedures (lapriscopic techniques, catscans) telephonics (cell and satcom technologies) office automation (PC's, fax, email) and mass communications (mpeg, jpeg, CD, dvd) were all made without Government help or regulation. Some of these technologies sprang up only after Government interference was removed via court case (cell phone technology specifically, in a famous Texas case).

I suggest that some wealthy British Operator simply take on his local CAA rep to court, and sue him in a civil court, and present him the bill for the revenue that was lost because a commonly available technology was disallowed.

SASless, you'd never know that I was a liberal, would you?

[NigD]

Nick

I beg to differ, with respect to the U.K , GPS approaches are not always accurate. You may have LAAS well set up but the U.K. doesn't.
I'm now waiting to get rather quickly corrected:D

NigD

[Q max]

There is no incentive for anyone to approve anything in the UK. There is only 'downside' for them - if it's wrong (or even when there's only the perception that it's wrong) they lose their job.

It's a structural problem - the regulators should be encouraged to make blameless 'best judgement' type decisions without fear.

This generic problem limits the business, to our detriment. - Kills aviation. FAA appears more pragmatic.

Nick - brave words but in the UK you could get 'grounded' just for thinking like that !

[MightyGem]

SASless, at last! You're getting the point of my original post. The last paragraph of your last post is what it's all about.:)

[GLSNightPilot]

NigD, LAAS & WAAS are still vapor. Don't exist in the US. But the GPS approaches are still accurate. The only requirement for augmentation is for precision approaches, not non-precision. Even the fixed-wing folks are flying GPS approaches, & we're flying them to points-in-space in helicopters to 300/1 at heliports, & 200/.6NM offshore. I've never, ever been off course on a GPS approach if the CDI is centered, & at airports, with the needle centered, you're over the runway, close to centerline. GPS approaches are much more accurate than VOR, & about the same accuracy as localizers. Should be the same in the UK or anywhere else.

[NigD2]

Stan

Yep, GPS is very accurate for non precision approaches. It would just worry me coming into an unusual airfield with crap wx etc relying on GPS alone to fly the approach. You have obviously used it very succesfully in the past but I still have reservations about its reliability.

Maybe I should invest in a spanner to untighten the bolt up my ass.................. or apply to the CAA for a job.

Nigd

[Nick Lappos]

NigD,

The accuracy of GPS is a known thing, and wrapped into the approach geometries, so you are correct, but it is not a reason to prevent approval.

For example, the bottom of the FAA non-precision GPS approach lane is about .9 Nm wide, with the course in the center. This accounts for the maximum RAIM error at the worst place in the approach. Most GPS hits are within 100 meters, so most approaches can be kept within a 0.1 NM width. The extremely conservative airspace protection is a product of the safety built into the approvals.

LAAS and WAAS are about to be sprung. A commercial WAAS receiver will be sold next year (I know because I am on the FAA/Industry committee to determine the procedures - we are meeting again on Wed of this week!)
The FAA has been pretty good about getting this stuff approved.

[Kalif]

Nick hits it on the head; just because the procedures don't exist does not mean that they are not needed. I seem to recall the CAA have, or had, a "GPS Steering Group"; quite what they do or did is a bit of a mystery,

The CAA should have in place a sytem whereby operators can submit for approval a let down based on a predifined criterea. It should ideally be designed with VOR/DME crosscuts and if available an NDB beacon. When flown, use of a radar service should also be utilized. With all these and the acccuracy of GPS then accurate GPS approaches are very possible and safe.

If the CAA does not get it's act together, (there's a radical thought), then unapproved procedures will be flown with various outcomes; the Irish S76!

As to the original thread. Allowed to fly at 300 feet? Maybe on scene and with 100 feet cloud seperation, but in transit - I would think not. Check the POAM!

[idle stop]

Just to reinforce the point the chaps made originally, whatever the legality or consequences for an aircraft making a GPS/VOR or suchlike approach without there being proper procedures, there is an elevated risk to the police or EMS operator of a mid-air when the police/EMs aircraft is operating legally in such poor weather.
Sorry, but if you see it being done, report it.

[john du'pruyting]

It seems that this thread has highlighted two issues.
1. The need for approved GPS approaches in the UK, or at least a method of persuading the CAA to start approving some of the unofficial ones more rapidly.
2. Some way in which an aircraft on an unofficial GPS letdown, can notify other aircraft in the vicinity of his intention to carry out such a letdown.
Now I appreciate that the sticklers will say that the simple answer is to stop those aircraft doing unofficial letdowns. That however is unrealistic for a number of further reasons.
1. The CAA don't seem that interested in doing it and have no real input into the private/corporate flight departments (as opposed to the AOC corporate flight departments).
2. The people utilising the services of these aircraft have paid serious money for the privilege and expect to get to their destination whatever the weather.
3. The guys/gals? flying those procedures are not going to make the customer/boss unhappy or risk losing their jobs.
4. It is in all our interests to ensure that helicopter aviation is successful. These guys may be pushing the legal boundaries, but if they succeed in making heli ops truly all-weather then that can only be good in the long run for the industry as a whole. If the legislators are turning a blind eye to it I don't see why fellow pilots should try and get it stopped, better to work out a practical system to co-exist with those guys safely.

[SASless]

Nick,

It is now apparant that graduates of Cobra Hall in Savannah must have been imprinted with liberalistic propaganda during a very vulnerable period in their life. Now, whereas, graduates from the Goldberg Stagefield of Cargo Helicopter dynamics and school of probability continium.....were imbued with conservative ideology early on......it is easy to see how you could take up for those bureaucratically burdened and freewill challenged sorts. Heheheheh!

[SASless]

NigD2.....care to start your reasons for being worried about doing GPS based approaches and why you think they are more unreliable/less safe than current ground based approaches? Have some of your graybearded colleagues explain the Decca approaches we used to do on a routine basis at sunny places like Sumbrugh.....and then rethink your answers.....I think you too would become a convert to this SciFi American thing. I defy anyone to convince me that the old runway 27 Decca Approach at Sumbrugh was anything but an unmitigated disaster (remembering I was doing it single pilot....sometimes sas'ed helicopter) usually at night and always in rat s_ _ t weather.

That particular approach required both a map change and a key change for the final approach.....I can safely state that I not once ever got it all done when by myself when in bad weather. I did find religion there a couple of times trying however!

[Shawn Coyle]

The issue with GPS approaches is to also make sure you have an IFR approved GPS. If you don't have RAIM, then it's like doing an ADF approach without monitoring the audio (what do you mean, you don't monitor the audio?).
Non-IFR approved GPS can wander off and not tell you. There is a whole different method (nearly said approach) to doing GPS instrument flying, and unless you know the whole thing, you are standing yourself and passengers into danger.
And a moving map GPS is far and away the best system to have.
Shawn

[GLSNightPilot]

Moving map? What's a moving map? I've never seen a moving map. How does that thing work? :eek: :D :D

I'd love to have one, but I thought it was great when I got a GPS with 2 lines of text. It's far better than the LORAN we used to use for approaches. It always (ALWAYS!) crapped out when the weather got bad. I trust GPS far more than VOR - the signal is far steadier & the indications are more precise, even at the VOR, never mind 30+ miles away.

[NigD2]

SASless

RAIM outages may occur due to an insufficient number of satellites or due to unsuitable satellite geometry which causes the error in the position solution to become too large. Loss of satellite reception and RAIM warnings may occur due to aircraft dynamics (changes in pitch or bank angle). Antenna location on the aircraft, satellite position relative to the horizon, and aircraft attitude may affect reception of one or more satellites. Since the relative positions of the satellites are constantly changing, prior experience with the airport does not guarantee reception at all times, and RAIM availability should always be checked. If RAIM is not available, another type of navigation and approach system must be used, another destination selected, or the trip delayed until RAIM is predicted to be available on arrival.

Not my quote but as in my last post I said I would have reservations about relying on GPS alone coming into an airfield with crap Wx and no alternative let down, as in the original posting of this thread

Hope this helps to show why I have my scaredy cat reservations

PS I have seen a GPS lose its signal on a flight test for an internally equipped GPS EGPWS....only once though.

[SASless]

So Nig...if you have an IFR certified GPS, with RAIM alert, then shy of a complete loss of signal....you accept the GPS more than meets the requirements for making an approach.....that is what I read out of Nick's post which also reports new and finer coming attractions here in the USA.

[[email protected]]

Chaps, I think some peeps have missed the point of Mighty Gems thread - a published approach to an airfield is safe because a) everyone knows where the aircraft will be because the approach direction is widely promulgated and b) has a proper approach minima based on obstructions on the approach path. An ad hoc GPS approach has neither attribute and despite the accuracy of GPS, it is downright dangerous to fly this type of non published letdown in congested airspace.
In an emergency or if you have got completely caught out by the weather with no fuel to divert, then you might have a valid case - but if you plan to do this type of letdown on a routine basis you should hand in your license an IR and go and do something else for a job.
If anyone out there is doing this type of letdown in UK then I hope it is not me you kill when you either have a mid-air or collide with a mast that you didn't know about.

[Q max]

(as for certifying them politics might have a part to play too)