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Wrong Altimeter Setting


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and quite a bit more ...  

BAe 125 struck trees after crew mis-set altimeter

  • 25 January, 2018
  • SOURCE: Flight Dashboard
  • BY: David Kaminski-Morrow
  • London

Pilots of an executive jet failed to set their altimeter to the correct pressure level before the aircraft descended low enough to collide with trees, investigators in Russia have determined.

The crew allowed the BAe 125-800 to continue descending despite automated warnings and the aircraft suffered substantial damage from the collision – some 18km from the airport – before the pilots aborted the approach.

Russia's Interstate Aviation Committee says the jet had departed Tyumen bound for Neryungri Chulman airport on 5 June 2016. It had been conducting the approach at night and had been following the RUGIL2 pattern, which involved flying south-east before turning left onto the 083° heading for runway 08.

The crew initially had difficulty contacting the local Chulman air traffic centre on 129.7MHz and instead reached the regional Neryungri centre on 121.7MHz.

This centre, upon the crew's request, cleared the flight to descend to flight level 90 (2,750m) before transferring the aircraft to Chulman tower control.

The tower confirmed the transition level as 2,450m and the airfield pressure (QFE) as 685mmHg, and allowed the aircraft to descend to 500m ahead of its turn towards the runway approach heading.

As the jet descended the tower asked the crew to confirm the QFE setting. While the crew replied with the correct number, 685, they needed to convert this to millibars – which would have resulted in a QFE of 913mb.

Instead the crew asked for confirmation of the sea-level pressure (QNH) to which the tower gave the figure of 1012mb.

The crew "did not recalculate" the airfield pressure of 685mmHg to give a QFE figure in millibars, says the inquiry, and instead set the altimeter to the QNH while continuing to descend.

This effectively meant that the altimeter was falsely showing the aircraft to be more than 800m above its actual height. Upon reaching the cleared height of 500m the aircraft would have still been indicating a height of more than 1,300m.

The enhanced ground-proximity warning system began to issue sink-rate and terrain alerts and, within a few seconds, ordered the crew to "pull up".

But the inquiry says the crew "did not follow the requirements of the flight manual" and instead continued with the descent. By the time the crew responded to the height warnings, the aircraft was flying so low that it collided with trees.

It climbed away despite sustaining damage to the leading edge of the wings, ailerons, horizontal stabiliser, and the engine inlets and fan blades. The collision partly jammed the elevator and the jet's left-hand winglet was torn off, says the inquiry, causing "considerable difficulty" for the crew as they tried to control the aircraft.

Inspection of the Aerolimousine aircraft (RA-02773), which managed to land without further incident, found that it had suffered impact damage to several other structures and system including its air brakes, radio altimeter antenna, and angle-of-attack sensor.

Investigators state that the crew's "delayed response" to the ground-proximity warning led to the collision with the trees. But it adds that there was "carelessness" in the treatment of the altimeter settings and that the crew had demonstrated that they had received "insufficient" training to carry out the flight.

Five passengers and a crew of three had been on board the jet, none of whom was injured.

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I wonder if barometric altimeters will be replaced by GPS altitude. And while they are at it, a switch to True and do away with magnetic.

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2 hours ago, JL said:

I wonder if barometric altimeters will be replaced by GPS altitude. And while they are at it, a switch to True and do away with magnetic.

In order to find True, do you not need to detect Magnetic, and then compensate for variation?

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15 minutes ago, conehead said:

In order to find True, do you not need to detect Magnetic, and then compensate for variation?

And the location of magnetic North is constantly changing. 

The magnetic North Pole moves in loops of up to 50 miles (80 km) perday. But its actual location, an average of all these loops, is also moving at around 25 miles a year [ref]. In the last 150 years, the pole has wandered a total of about 685 miles (1102 kilometers).

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I don't believe any GNSS based system cares about the magnetic pole. I would venture a guess that it adds the magnetic variation so that the portrayed tracks match what is on your maps and plates.

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Talk about thread drift...

But JL started it, and here we are.

First, dealing with the thread title, our "altimeters" are nothing more than barometers. In North America (and largely North America alone), we use a local altimeter setting when below 18,000'. In most other parts of the world, to alleviate the necessity of continuously resetting an altimeter (below 18,000') enroute, a "transition altitude" is used to switch to 1013.25mb/29.92"/Hg. Once enroute in most other parts of the world, there is no requirement to reset one's altimeter unless a change to a mountainous region or some other vast geographic feature requires it until ready to start desecent to destination airport.  So we fly "barometric settings" vs true altitudes.  Only a few years ago, GPS altitude had the same errors as lateral position errors. When GWB removed Selective Availability from GPS constellation position information, and since with the supplementation of GLONASS and other positioning satellite constellations, that error ( +/-50') both lateral and vertical, was reduced to less than 5'.  So in direct answer to JL's question, yes, "GPS" altitude is more "accurate" with regards true altitude than its barometric cousin.

Then there's this:

The worldwide use of the magnetic north pole as a guidance to navigation is an anachronism, and should be abolished, permanently.

In the next 50 years, in all likelihood, the earth will develop multiple magnetic "poles" due to the cataclysmic geological phenomenon in which we are in the midst - the toppling of the iron core.

This is an event that has happened many times in the past, but only in geologic times, i.e. 50 - 500,000 years.

NavCan actually proposed an end to the use of magnetic direction finding.

Yabut, what does that mean? It means that the earth, in its orbit, in its internal composition and in its rotation, is nothing more than a planetary dynamo - "generator" as it were. Grade 10 Physics. What does it mean for our survival as a species? (Now THAT is a bigger question than "climate change", dontcha think?) It means that the magnetic field surrounding our planet can deflect enough solar radiation to allow life, as we know it, to continue on our Pale Blue Dot.

What would happen to us if at some point our magnetic field nullifies itself?



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