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Lessons Learned / your most scary flight

If you are flying an ILS down to 200 ft wouldn't you prefer a current airfield-specific pressure setting, (QNH or QFE), rather than a regional QNH designed for terrain clearance over a wider area, updated "fairly often"?

I don't know many ILS approaches where you won't be given a QNH. One tends not to do them on an area QNH.

EGTK Oxford

If you are flying an ILS down to 200 ft wouldn't you prefer a current airfield-specific pressure setting, (QNH or QFE), rather than a regional QNH designed for terrain clearance over a wider area, updated "fairly often"?

I don't know why people are so QNH obsessed. It's inaccurate and error prone. Ever since I had a clogged static port on one side of my plane and performed an approach in IMC where I got way too low because of a strong side wind, I have started using the GPS altitude as my reference and constantly compare it to what my altimeters show. I don't want to be killed by a clogged static port.

GPS altitude is far superior to anything barometric. Just yesterday I had a long cross country flight with fluctuating pressure (several high and low pressure areas) and the aircraft was riding up and down, burnings loads of fuel just to remain on the 1013hPa pressure level. Aviation could greatly benefit from replacing barometric altitudes with GPS altitudes.

Aviation could greatly benefit from replacing barometric altitudes with GPS altitudes.

Well the problem is that everyone needs to be on the same reference. Sadly this won't easily change.

For me, I use radar altimeter when close to the ground!

EGTK Oxford

I don't know many ILS approaches where you won't be given a QNH.

I have only come across it at RAF Benson.

In general I would prefer to have QNH, but not so much as to ignore a QFE if that is what is given to me by the Approach Controller!

Booker EGTB, White Waltham EGLM

I don't know why people are so QNH obsessed. It's inaccurate and error prone

A great point regarding accuracy, and I have often said the same thing e.g.

(a very typical example, to be within 10-20ft) but as we all know one uses baro altitude for traffic separation, etc. It isn't going to change.

If I was flying an IAP and the GPS altitude (Garmin 496, EGNOS) differed significantly from the altimeter, and the wx was bad enough, I would initially query the QNH and then would fly to somebody's ILS and land on that.

It's interesting about flying uphill. Of course this is true, as e.g. the sloping line here

shows, but what is the real gradient? Let's say you cross 6 isobars i.e. 24 millibars over 500nm, that is about 700 feet of climb, which is a gradient of 0.024%. Hope I got that right! It doesn't seem very much.

I have only come across it at RAF Benson

In my very limited experience of flying IAPs to RAF bases, they would not give me the QNH.

Administrator
Shoreham EGKA, United Kingdom

In my very limited experience of flying IAPs to RAF bases, they would not give me the QNH.

Strange. Among the ones I remember having been to are Northolt and Biggin Hill. Both gave us QNH when we asked.

But coming to the original subject: One of my biggest blunders - and close calls - was also altimeter related. I was flying some guys to an important family event (wedding maybe) VFR in a C340, single pilot. A very short trip, 15 minutes only, but they took the earliest scheduled flight to Stuttgart and continuing by car would have made them arrive late. So the owner of the 340 asked me if I could collect his relatives from the passenger terminal and fly them to his event as quickly as possible. And also, I assume, because he wanted to show off: "Look, I got myself an aeroplane and a pilot"! It was in the mid nineties, steam gauges, no moving map, just a very basic GPS giving me bearing and distance to our destination, the very VFR airfield at which "achimha" is based.

Just when I left our control zone on a special VFR clearance, the clouds got so low that I chose to fly through them (verboten in this part of the world - no IFR outside controlled airspace) rather than below them, because flying below 500ft AGL would have been even more verboten... It was Sunday morning in very marginal VFR weather and the chances of colliding with anybody else flying "YFR" were marginal too. Getting closer to our destination, I intended to descend gradually until coming below the clouds. The first step was going to be back down to 3000ft (field elevation is something like 1500ft with close-by obstacles rising above 2800ft). This aircraft had the most horrible altimeter I have ever come across, a pseudo-digital drum type thing with a single pointer that most unconventionally did one full turn every five hundred feet (the closest I could find with a google search is this one here: http://aviation.watergeek.eu/images/f-4b/f-4-altimeter.jpg but this has the usual 1000ft per turn pointer). So when it had done it's two turns and I could read the new number on the drum, instead of 3000ft I found myself at 2000ft. I had misread the bl**dy thing by a full 1000ft! Still in clouds and not really sure where I was in relation to terrain and obstacles of which all I knew was that they were above us... The next few seconds were spent getting the highest rate of climb out of this aeroplane that it has ever seen in it's life (it still flies in the US as N487KM, the very registration under which we ferried it across shortly after these events). I then continued to the field by GPS and slowly spiralled down in the overhead until we got below the clouds which were less than 500ft above ground level. The first thing I did after the passengers had left was phoning in a Z-flightplan for the return trip... A few years earlier, in 1989, a Cessna 421 had crashed into a hill flying to the same destination in very similar weather with just a few miles to go claiming seven casualties. It could have been me.

EDDS - Stuttgart

Still in clouds and not really sure where I was in relation to terrain and obstacles of which all I knew was that they were above us.

I think I started my PPL way too late. Today even with the best GPS / glass cockpit such stunts are unheard of

A few years earlier, in 1989, a Cessna 421 had crashed into a hill flying to the same destination in very similar weather with just a few miles to go claiming seven casualties. It could have been me.

They recently retired the TGO VOR south of EDDS so the deadly EDTH-TGO is no longer a risk...

The worst ever for me was the clogged static port I mentioned. I got into a strong cross wind during approach and the clogged port was in the wind making the static system show about 500 ft more than it should (all altimeters, glass cockpit and transponder). It was a non precision approach with 600 ft MDA so this could have ended badly.

Another blunder was a misconfiguration of the very unintuitive GNS430. I wanted to let the AP fly the ILS and was vectored onto it (mountainous terrain). I had loaded the approach and coupled it to the AP. However, I made the small mistake (not the first time) of choosing "Load?" instead of "Activate?" in the GNS430 and this made the difference of not slewing the course pointer on the EFIS. When I was on the ILS, I switched the GNS430 to VLOC and the AP to NAV. The result that it was trying to fly me into the mountain (in IMC). I noticed because it did not turn how I expected and I have a 2nd GPS running alongside but I could have missed that for a second too long. Configuring the GNS430, the glass cockpit and the AP correctly is not straightforward.

In my early days with the TB20 and with an instructor, we flew into Exeter EGTE for an ILS. He didn't know anything about the avionics (despite claiming to have an ATPL - falsely as it turned out) and at that time neither did I, and we "intercepted" the localiser with the NAV/GPS switch in GPS mode

It actually wasn't all that far off in terms of bearing, because the last GPS leg wasn't far off the LOC inbound track, but the glideslope didn't come up because the LNAV came from the KLN94 and that has no VNAV output.

Oddly enough I flew the other day with somebody in his TB20 who has a GNS530 and since that contains the LOC/GS receiver, the NAV/GPS switch doesn't do anything. You can press it, but it doesn't work as a switch anymore; it is merely an annunciator. He has an EHSI and that does the NAV/GPS switching. Tuning an ILS frequency on the GNS530 makes the NAV/GPS "switch" indicate "NAV", I think. This stuff can be quite tricky... it makes one realise just how much systems knowledge we need to operate our "little" planes safely.

Administrator
Shoreham EGKA, United Kingdom

how much systems knowledge we need to operate our "little" planes safely.

Which leads me to the rhetorical question whether the current avalanche of electronic "aids" has sufficient added value to make up for the risks of confusion, malmanagement and malinterpretation. But I suppose that argument has already been done to the death, here and elsewhere, a zillion times?

Can't help remembering the old Confucianism (hehe, why aren't there any new ones?) "a pilot with an altimeter knows her/his altitude. A pilot with two altimeters is never sure."

EBZH Kiewit, Belgium

Which leads me to the rhetorical question whether the current avalanche of electronic "aids" has sufficient added value to make up for the risks of confusion, malmanagement and malinterpretation. But I suppose that argument has already been done to the death, here and elsewhere, a zillion times?

It's the price one pays for the greatly increased mission capability of IFR.

If you stay 100% VFR then you can fly with just a map and compass

Administrator
Shoreham EGKA, United Kingdom
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