View Full Version : Height Readout Question.

Noah Zark.
24th Apr 2014, 00:35
Excuse a question for you professionals from a non-aviation SLF, but in many flight deck videos showing a landing being carried out, an automated voice can be heard calling out the decreasing height i.e. '200 feet, 100 feet, fifty feet' etc.
What I am asking is, exactly what is at the heights as they are called? Is it the main undercarriage, the tailskid, the captains head? In other words, what is the datum used in these callouts?
Thank you.

24th Apr 2014, 00:38
Main undercarriage.

24th Apr 2014, 07:15
Captain's head would be a good point of reference, too, actually? :E

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcQ6CNjBKqyoVheWIQBI3Rz9TbbYegEzhWd7G2orRnQ Z-o4TsfcD

Shaggy Sheep Driver
24th Apr 2014, 09:14
On Concorde the radio altimeter transmitters and receivers are mounted under the belly of the fuselage about half way down. They may well be calibrated to compensate for the height difference between there and the mainwheel tyres with the gear fully extended (unloaded). But as they are mounted some distance in front of the main gear, the actual height difference between the tyres and the RA sensors will vary with pitch attitude.

24th Apr 2014, 09:25
Underneath the fuselage (obviously) near the main gear on our lil jet. :)

24th Apr 2014, 09:27
They are calibrated to read zero on touchdown and with the aircraft in the landing attitude.

As the nose wheel is lowered the reading becomes negative.

The sensors are normally under the fuselage between the nose and main gear.

Lon More
24th Apr 2014, 09:37
In my case, distance to go to the scene of the accident would have been more appropriate.

We'd lost contact over the years but just heard that an old friend and instructor had passed away last year at the aage of 82. He was instructing almost up to the end.
Jan Minoli got his wings in 1956 in the Dutch Airforce. Later he trained some 2000 glider pilots, 2000 PPLs and 1000 CPLs and ammassed 35000 flying hours in his 65 year career.. A true gentleman and a great instructor Rust zacht Jan

Noah Zark.
24th Apr 2014, 12:49
Thanks for the replies and the info, folks!
N.Z. :ok:

24th Apr 2014, 13:09
At what altitude does the Airbus call you a mental incompetent?

Lon More
24th Apr 2014, 14:17
At about 1:33 in this video

landing - YouTube

Krystal n chips
24th Apr 2014, 18:40
NZ....this should answer your question.....there again, you may become even more confused.....it does get a bit complicated at times....;) :)

Radio Altimeter Tech Ops Forum | Airliners.net (http://www.airliners.net/aviation-forums/tech_ops/read.main/24197/)

I am sure however, that former Concorde pax are thoroughly well versed in the technicalities if you need further clarification.

Noah Zark.
25th Apr 2014, 11:26
Thanks again, folks!

25th Apr 2014, 13:34

Thanks for the note on Jan Minoli (RIP). A real character and outstanding pilot. Did my PPL with him at EHBK back in 2000-01. In those days he was hoping to keep his medical / flying until he was 80. I am so glad he made it. Always recall his banter with ATC as we practiced steep-turns over his friends' houses inside the Maastricht CZ.

I understand he was one of the first Dutch Air Force Meteor pilots - in the days before they had ejection seats. On two occasions, after engine failures, he crash landed after sorties out over the North Sea. Apparently a colleague had tried to bale out once with the regular parachute, was knocked unconscious by the tailplane, and died. A true advocate of "fly the plane until the last part stops moving!" (Though I later heard that the reason for the crashes was fuel starvation!)

A real gent, great pilot and friend. He will be missed. :ok: