Discuss the problems and solutions to all of the situations that Pilot X finds himself in.
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By G-BLEW
#879431
Height of absurdity

Richard Boswell shows how even an experienced professional pilot can make basic errors if relying too much on instinct. Pilot X is out of practice, and forgets checks that every PPL should know inside out

As X settled into the pilot’s seat he felt at home once again. His hands easily located the harness buckles and he instinctively strapped himself in while chatting to the examiner. Once comfortable, he started to run his eyes and hands around the cockpit as he completed the pre-start checks. Only the occasional hesitation hinted that he had been driving a desk for the last year. This was his first time back in the helicopter as he revalidated his professional licence.

X had known the examiner sitting beside him for many years. They had worked for the same company in the past and had completed their training to become instructors and then examiners around the same time. As a result, they had often carried out proficiency checks on one another; with over 12,000 flying hours between them, they trusted and valued each other’s professional opinion. X had chosen a career move which took him away from flying professionally while his colleague had continued to fly as a senior training captain. They had not seen each for some time, so there had been plenty to catch up on before the pre-flight brief.

X took his time over the checks. Not only was he revalidating his licence, he was also renewing his Instrument Rating and the plan was to spend the first part of the flight ‘under the hood’ as they completed an ILS followed by an NDB approach. With the checklist on his knee, he carefully ran through the full IFR checklist for the EC135 helicopter. With the glass cockpit and modern autopilot, there was a lot to run through, so he elected not to even attempt the checks from memory. He also took the time to identify as many of the navigational aids as possible. Experience had taught him that getting this out of the way early, in the calmness of the cockpit, with the helicopter still on the ground, was a sensible thing to do. It took almost 30 minutes to start the helicopter and complete the checks but having completed it all in slow time he now felt ready for the flight.

Lifting into the hover he managed to avoid the overcontrolling that was common to new pilots and he felt comfortable, despite the lay-off and the fact that only 100 hours of his 6,500 were on this particular type.
It felt good to be flying again. Many times during the last year he had regretted climbing the career ladder and leaving the joy of full-time flying behind him. As he hover taxied to the departure point he yawed the nose left then right, checking the instruments. He surprised himself by how quickly he was settling back into the routine.

Cleared for take-off, X lowered the nose and gently applied power. The helicopter accelerated slowly as he gently handled the controls. As the electronic ASI on his primary flight display flickered into life and passed through 30kt, he called, “Take-off decision point,” to the examiner. Safely climbing away at 70kt, the examiner took control and asked X to fit his foggles for the instrument flying. It hardly seemed necessary as they were quickly in cloud, but the examiner needed to ensure that he witnessed X instrument flying the approach down to the published minima.

Perishable skills

Concentrating on the instruments, X now found that he was working much harder than before. They had briefed that the autopilot would not be used for any of the flight – and X knew that instrument flying was one of the most perishable of all piloting skills. Instructed to level at FL35, he found himself ballooning above the cleared level; as he attempted to correct this, his heading wandered off by 30°. Correcting this, he descended 100ft below the level. It quickly became apparent that he no longer had any spare capacity to continue the conversation with his examiner.

He had requested a radar vector to an ILS for the first approach, as he had known it would take a while to settle back into the swing of things – he hoped the slightly less demanding ILS procedure would help sharpen his flying skills before he attempted the more demanding NDB approach. He also knew that at some point the instructor would simulate an engine failure and that too would increase the work rate significantly.

Like all international airports in the middle of summer, the airspace was busy and the radio calls came in thick and fast. X was given a new heading and cleared to descend to 2,500ft on the QNH, which he was given. He was cleared for the approach and asked to call when established on the localiser. A year ago, processing this information would have come instinctively but now he had to apply conscious thought and as he did so he lost accuracy in his flying.
X was very grateful he had all of his experience to fall back on. He was quickly established on the ILS and for most part the needles remained in the centre of the dial as he descended towards the runway.

The decision altitude was 320ft. As he passed through 1,000ft the ILS needles were already very sensitive. As he passed through 500ft things just didn’t feel right. “I have control,” came through the intercom.
X glanced at the rad alt for the first time and noticed that it was passing below 100ft. His heart sank. He could not believe that as such an experienced aviator he had made such a schoolboy error.

1. What did X fail to do which resulted in him inadvertently descending well below the published decision altitude?
2. How should have X set up the rad alt to have helped prevent this?
3. What is the procedure for confirming that your altimeter is serviceable?
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By KNT754G
#879504
1) it would appear that X never correctly set the altimeter. I would have thought the checklist should have highlighted this error.
Also there would be a point on an ILS approach where range is checked against altitude, outer marker on an old fashioned approach or a range/DME/Altitude check with an ILS/DME.
2) Not familiar with RADALT so not certain of my stance in answering this.
3) Pre flight, zero the needles (indicate zero height), note the reading. Add ten millibars (or hectopascals) to the subscale, note that indicated level is now 270' +-50.
Subtract 20 millibars (original - 10) level indicated should now be -270 (+-50 again).
Set subscale so that altimeter indicates present altitude (most likely apron altitude) and note reading. QNH should be +- 1 Mb from this and must be no more than +- 2 Mb from this figure.
By AttorneyAtLaw
#879519
There does not need to be anything wrong with the altimeter. X has been exhibiting difficulties previously in maintaining his scan. Now, on the glide slope with the needles very sensitive he has focused entirely on keeping the needles central and has failed to maintain his scan. Assuming he was descending with a ground speed of say 70 knots, his rate of descent would be 350 feet per minute. At this rate it takes just 30 seconds to reach decision altitude from 500'. He has let the aircraft get away from him. It is also possible that although given QNH he failed to reset the altimeter, which may have been set for QFE.
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By Keef
#879529
... or maybe he got it wrong earlier, when he was joining the glidepath, and is on one of the side lobes of the glideslope. That would make it extremely skittish!

If at the IAF the altimeter indicates correctly, and you checked it (as KNT says) before departure, and rechecked the QNH/QFE before commencing the approach, then all should be well. I've never used a radalt, but I would expect to look at it when at the IAF and see a sensible reading.
By AttorneyAtLaw
#879532
Can you not set the rad alt to give an audible warning at DA? That would have been an additional cross check.

Bearing in mind that he had vectors to the ILS would this not make intercepting one of the lobes unlikely?
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By dublinpilot
#879549
The article states that pilot x was instructed to fly at Flight Level 35. However it doesn't state that he changed his altimeter setting to 1013.
Likewise it doesn't indicate that he changed back to the QNH in the desent .

It is possible that pilot x did indeed change their altimeter setting to 1013 to fly FL035, but failed to change it back to QNH in the desent. If there was a significant pressure difference on the day, the flight level reading on the altitmeter could be quite different to their actual altitude.
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By Keef
#879588
AttorneyAtLaw wrote:Bearing in mind that he had vectors to the ILS would this not make intercepting one of the lobes unlikely?


It would make intercepting one of the lobes of the localiser very hard to do, but wouldn't prevent a lobe of the glideslope.

I've not (as far as I can recollect) ever seen an "underneath" lobe on a glideslope, but I've certainly seen an "above" one when going missed.
By johnm
#879660
I've not (as far as I can recollect) ever seen an "underneath" lobe on a glideslope, but I've certainly seen an "above" one when going missed.


That's why you join the glideslope from underneath at a predetermined altitude and distance isn't it?

It would appear that Pilot x failed to deal with altimetry correctly and failed to set the alarms on the rad alt (not that I know much about rad alts except for what I crammed and then forgot for the IR exams).

If there's no DME it's too easy to follow the needles and not cross check time for distance. (I know I keep getting b0ll0cked for it)
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By KNT754G
#880036
AttorneyAtLaw wrote:There does not need to be anything wrong with the altimeter. X has been exhibiting difficulties previously in maintaining his scan. Now, on the glide slope with the needles very sensitive he has focused entirely on keeping the needles central and has failed to maintain his scan. Assuming he was descending with a ground speed of say 70 knots, his rate of descent would be 350 feet per minute. At this rate it takes just 30 seconds to reach decision altitude from 500'. He has let the aircraft get away from him. It is also possible that although given QNH he failed to reset the altimeter, which may have been set for QFE.

But the saga states
As he passed through 500ft things just didn’t feel right. “I have control,” came through the intercom.
X glanced at the rad alt for the first time and noticed that it was passing below 100ft.

clearly indicating a mismatch between indicated and actual altitude, even allowing for any airfield elevation since DA had been calculated as 320'
By AttorneyAtLaw
#880143
clearly indicating a mismatch between indicated and actual altitude, even allowing for any airfield elevation since DA had been calculated as 320'


Not necessarily. It is quite possible that he was so focussed on the glideslope needle that he just descended too low. There does not need to have been any incorrect setting of the altimeter. He may well have seen it pass 500' but then not kept it in his scan. The article merely tells us what the height was from the rad alt, not what his altitude was. I agree though that a failure to reset the altimeter could also have been a factor if the pressure was lower than standard. It is surprising though if that was the case that the error was not picked up when receiving radar vectors for the ILS as he would have been continuously too low.
Last edited by AttorneyAtLaw on Fri Jul 23, 2010 8:27 am, edited 1 time in total.
By mixsfour
#880267
I reckon he forgot to re-set QNH when descending from Flight Level. Or maybe he forgot how to set the electronic one. Weather conditions suggest QNH would be lower than standard atmosphere. "high to low, down you go"

I was taught to set the airfield elevation on the altimeter then compare the indicated pressure setting with the QNH given by the tower as a rough serviceability check.

Set decision height on RA then you get an audible alarm if you go below.

Check height against DME, approx 300ft/mile as someone else said.

If this was his first flight for a year I don't think he should have gone straight for IR revalidation without some "de-rusting" sessions first.
By Tony Hirst
#880547
X probably failed to set the QNH from standard on the altimeter. Given there was no indication of a bust previously in the flight then I assume this was the case. However, crucially and as previously said, X failed to cross check the ILS glidepath against the altitude and the DME. This check should be performed no later than the FAP.

You could set the DA on the rad alt to get an audible/visual notification. However, certainly at my company, that is not SOP as a Cat 1 approach is based on the barometric altimeter and that is your only true reference for the decision height. It may seem sensible to set the DA on the rad alt, but it maybe higher or lower than the barometric DA, neither of which is useful and also potentially distracting at a critical time. I would guess, especially over a final approach with uneven terrain.

For the altimeter I was taught +50/-75 of airfield elevation during my PPL. Currently our company/aircraft limitation is +/-75' of the airfield elevation.
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By G-BLEW
#883885
Not used a rad alt but wouldn't it show height rather than altitude?


Indeed it would/does.

Ian
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By Morley
#884833
Miscalculation of DA? 320 feet above msl appears ambitious. If it was Blackbushe they would be on the threshold. So, either its a coastal airfield where QNH = QFE or I have misunderstood the article. It appears to suggest that 320ft QNH is 100ft AGL. If that is the case pilot X didnt calculate DH or mistook DA for DH. Why have these acronyms only got two letters? Thats the reaL question here!