HUMBERSIDE TAXI ACCIDENT (PART 1)
Thank you to those who participated in this exercise which was to comment on the AAIB report and I apologise for the very long delay in publishing this. In Part 1 I will just deal with the errors and the areas overlooked in the report, as I see them. Disappointingly none of you who responded discovered any of these points.
The reason I took issue with the AIIB inspector, CAA and NATS is that there is supposed be a big drive towards attempting to reduce the number of runway incursions and all of these agencies are supposed to be involved, pause for laughter! Runway incursions are caused by TAXIWAY & RUNWAY MOVEMENT ERRORS (anyone remember Tenerife?). When you read the following article just remember that 583 people lost their lives in March 1977 because of a TAXIWAY & RUNWAY MOVEMENT ERROR. It’s disappointing to note that several of the people I have contacted about this incident have shown an attitude not too dissimilar to the pilot responsible for the Tenerife disaster, Captain Jacob Van Zanten!
First a brief overview of the accident again
A Piper Saratoga was parked on the grass light aircraft parking area at Humberside Airport facing approximately 020 degrees. (we are not told exactly where the aircraft was parked)
It was the 61-year-old PPL holders first visit to Humberside, he was in current flying practice and had a total of 671 hours of which 300 were on type. He requested detailed taxi instructions and he was initially given instructions to join the grass taxiway towards Runway 08, but the controller subsequently decided there may be insufficient room for the aircraft to taxi safely along that route. The controller then amended his instructions, intending to route the aircraft to Runway 08 via hard taxiways. The pilot, it seems, became confused by the new instructions and inadvertently left the grass parking area perimeter edge prematurely, even though apparently signage was present to prevent this. After joining the fire vehicle access road and thinking it was part of the cleared routing, he subsequently collided with a roadside sign.
The accident was subject of an AAIB correspondence report, which can be found here AAIB REPORT
The black X in the above image shows the area where I think the accident occurred. Notice the lack of yellow centreline markings in this area as this is the fire service access road. The yellow centreline markings start from the concrete spur taxiway further along to the north and this is obviously where ATC expected the pilot to leave the grass and join the taxiway. The Airfield manager however says that this concrete spur isn’t in fact the normal way of leaving the grass parking area and only available to local based aircraft and that’s why the taxiway is undesignated! You see its a secret taxiway! Umh,sounds to me like making up rules as you go along. A taxiway with a yellow centreline marking is a taxiway at the end of the day and there is no mention of it not being available to visiting aircraft in the IAIP!
Looking at this aerodrome chart and the LIGHT AIRCRAFT PARKING AREA how would you get off the grass if you were trying to work this all out at the preflight stage? The only access is by what is shown on this chart as a vehicle access road in the north-west corner, the concrete spur, the very taxiway that ATC told the Saratoga to take. There are no access points shown around the perimeter of the complete parking area except the concrete spur taxiway. On the eastern side of the parking you will see a gap between the grass taxiway and the parking area, if you feel that you could taxi across that does that also mean you could carry on across the grass taxiway in a straight easterly line towards the runway as it’s the same light green colour- I don’t think so! (we will discuss this more in part two)
But help is at hand!
The Humberside parking and docking chart shows that you can in fact leave the light aircraft parking area directly onto the grass taxiway but notice where taxiway ECHO ends on this chart then look at the other chart. The aerodrome chart shows Taxiway Echo ending at the fire station apron, this chart shows it ending at the grass taxiway. Confusing isn’t it but when I pointed this out to the AAIB inspector he said there were not any problems with the Humberside charts? Hope he is a bit more thorough when he investigates a real accident!
These links may not work so go to www.ais.org.uk/ and then to to the IAIP, then to AERODROME INDEX SPECIFIC and look at the Humberside charts.
We have been using this Humberside incident as a ground movement (Ex 5) training exercise for the last two years on both PPL & Flying Instructor training and I also threw it open to all 2000 of you via my internet blog for comment and again I apologise for the long delay in publishing this article.
Unfortunately no one who responded to my questions came up with the relevant answers to the errors that are contained within this report although everyone who responded agreed that the inspector’s report was difficult to understand in relation to where the aircraft was parked and how it got to the point of impact with the sign, with several commenting that a diagram would have been useful. Most of you mentioned some ambiguity and misunderstanding of the ATC instructions.
So here are the errors or points (as I see them).
1.TAXIWAY INCORRECT COLOUR ON NATS AIS CHART
The taxiway that the pilot was supposed to use was not (and is still not) shown in the correct ICAO colour (taxiways are sand coloured) on the aerodrome chart. This taxiway is still in use, as confirmed by ATC on the 8- 8-2016.
At the time of the inspector’s report the taxiway was shown in white, as it is now, this is, to my understanding, the colour for a vehicle roadway. This should have been picked up by the inspector and all of our respondents. When you inspect an aerodrome chart for taxi planning purposes it is essential that you can differentiate between dedicated vehicle routes and established aircraft taxiways. The way that you do this is by colour although several airfields that I am aware of have a confusing lack of sand colour on routes that are taxiways! The taxiway from the eastern end of the hangar at Shobdon and some taxiways near the hangars at Gloucester for instance.
Another give away at a licensed or certified airfield, when you actually taxy, is that dedicated vehicle access routes DO NOT HAVE YELLOW CENTRELINES, if you are on what appears to be a taxiway and it has a white centreline, you are on a vehicle roadway! (this is rarely pointed out to PPL students!). It would have been appropriate and helpful if the inspector had mentioned this in the report too!
AIP GEN 2 GEN 2.3-2 (scroll down) shows the ICAO colours for taxiways, although note that NATS AIS do not follow these colours on the parking and docking charts!
- INCORRECT COLOUR OF GROUND MARKERS
The inspector’s report states;
The boundary between the parking area and the access road that the aircraft crossed was marked by seven low-level signboards with arrows pointing towards the access ramp. There were also triangular black-and-white striped ‘bad ground’ markers between the signs, warning pilots not to join the hard surface in that area.
Amazingly not picked by any pilot so far, or the AAIB inspector, was that the black and white striped bad ground markers are the WRONG COLOUR. The bad ground markers in this situation should be in fact orange and white. Black and White marker boards mark runway displaced thresholds and therefore should not be used for marking bad ground see Chapter 6 page 7.3 – CAP 737 Visual Aids Handbook This is basic PPL Aviation Law knowledge!
After several emails the Humberside airfield manager finally replied to me and said they had changed the colour of the markers to the correct colours after my email! He would not respond to any of my other comments but stated that the charts would eventually be changed but it could take some time!
- NO TAXIWAY DESIGNATOR
The dedicated concrete taxiway from the grass parking area, as shown on the Humberside aerodrome chart, does not have a taxiway designator letter which I find very unusual for a licensed airfield especially as CAP 168 states that all in use taxiways should have a letter designation. Although there does not seem to be any common policy for this and it is difficult to tell if some taxiways are for aircraft or vehicles. (parts of Shobdon and Gloucester for instance).
CAP 168 states
Taxiway location signs
7.41 Taxiway location signs should be used to identify individual taxiways.
7.42 All in-use taxiways should be designated by a letter of the alphabet
With no taxiway designator how do you look up a specific taxiway in the IAIP? In fact this taxiway is not mentioned in the IAIP entry for Humberside.
Designators also reduce ambiguity and confusion and it could be that the lack of a taxiway designator may have contributed in causing in some confusion for the pilot at Humberside. This was the RT question received by the pilot from ATC,
“CAN YOU SEE THE CONCRETE STRIP ON YOUR LEFT HAND SIDE?”
The pilot replied that he could, so the controller instructed the pilot to take it, and then Taxiway Delta.
If you look at the charts and especially the Google Earth presentation you can see that the concrete fire service access road (on the pilot’s left) looks like a continuous road to taxiway Delta but it in fact changes to a taxiway at the neck of the short spur but it remains concrete throughout and hence the possible confusion.
Ambiguity was most likely also compounded by the word ‘STRIP’ which as far as I am aware is not a word that is contained in CAP 413 in relation to taxi. The controller obviously meant the short piece of concrete taxiway that extended out from the access road and the beginning of the mystery taxiway proper (the spur) but the pilot obviously interpreted, ‘STRIP ON YOUR LEFT HAND SIDE’, as the concrete fire service access road even though there were ground markers to prevent premature taxi movement onto this road. Either of these metalled surfaces could be described as a strip! Again no one commented on the use of the non standard word, ‘STRIP’!
The report states; In the ATC tower, some 800 m away, the controller became aware that the aircraft was not exactly where he first thought, so warned the pilot “THE CONCRETE IS A BIT FURTHER ALONG THAN THAT” to which the pilot responded, “AH YES I CAN SEE IT NOW”.
Unfortunately ‘CONCRETE’ throws up another ambiguity because the complete vehicular road and mystery taxiway appear (Google Earth) to be of the same surface material, concrete!
Standard unambiguous phraseology is essential to prevent misunderstanding.
The pilot eventually replied “OK, I GUESS. IT’S A BIT NARROW BUT I’LL HAVE A GO”
The last call should have possibly alerted everyone that something was amiss and maybe also trigger some alarm bells with the pilot! The professional safe operation of an aircraft is not about ‘having a go’, it’s about managing the aircraft safely from one position to another using all the available information!
Why does this taxiway not have a specific taxiway designator letter? Note on the present aerodrome chart part of this mystery taxiway is obscured by the D2 holding point sign making preflight taxi planning even harder. This D2 sign should redrawn somewhere else.
For preflight planning (taxi) purposes, if I look at the aerodrome chart (using correct colours) the only way seemingly to get off the grass parking area at Humberside is via the southerly ECHO taxiway but if I look at the parking and docking chart I can only get off the grass parking area via the eastern edge of the parking area to the grass taxiway!
- Chart Anomalies
The Echo taxiway (south of the grass parking area) is shown as being a continuous aircraft taxiway all the way to the fire service access area on the aerodrome chart but if you look at the satellite picture on Google Earth the yellow lines seem to stop a long way before the fire service access area and are replaced by white lines. This was the case at the time if the accident report. So unless I am mistaken the aerodrome chart is in error here and the taxiway should not be shown entering the fire service access area.
However If you now look at the AIS aerodrome parking and docking chart this shows Taxiway Echo ENDING at the grass taxiway. In contrast the aerodrome chart shows it extending past the grass taxiway into the Fire Service Access area!
All the above points should have been dealt with by the AAIB inspector but when I wrote to him about this matter he was quite rude and obstructive and dismissed any suggestion of mistakes and refused to make any further comment. All of our respondents also agreed with me that the report did not make it usefully clear where the aircraft was parked and how it reached the board that it hit but again the inspector disagreed.
We are not told if the pilot completed pre flight planning which included looking at the appropriate AIS or equivalent chart of the parking area because the AAIB inspector apparently did not ask for any further information and merely relied upon the information as supplied to him by the various parties mentioned above. This I understand is standard procedure for an accident where there is no injury.
I cannot see the point of having AAIB inspectors looking at or getting involved with accidents like this as all they do is write up what the pilot wrote in his report and that’s hardly an investigation and this type of accident is already covered by the CAA Mandatory Occurrence Reporting Scheme (MOR). By giving no advice to prevent re occurrence, as the AAIB charter states that they are supposed to do, it might as well just be an MOR. As you can see from my article there is plenty of advice this inspector could have given if he had taken the time and trouble to do so.
We will look at how you can prevent such taxi errors in Humberside Part 2-coming shortly!