October's Instruments Exam

[james_davis]

One question that came up in the ATPL Instruments exam today (Tuesday) was about the Pitot Tube.

The question asked (amongst other things) why the pitot tube is located away from the surface of the aeroplane. Two of the answers were a) to make sure it is away from the boundary layer and b) so that it is in the undisturbed airflow.

Both these answers seem to be pretty similar, has anyone got anything definite on this?

[Whispering Giant]

I've allways been told - from several sources that it is answer B - so as to keep the pitot head in an undisturbed airflow.

W.G

[NineEighteen]

I'd say option (b) too because it's important that it's in undisturbed airflow. I'd only really consider the boundary layer with respect to the lifting characteristics of the wings (PoF).

Having said that, you are correct, the options are not that dissimilar. I wouldn't stick a pitot tube in the boundary layer either because, by definition, the airflow closer to the airframe will be slower that in the freestream. I guess in practice, the boundary layer is quite shallow and so it can be ignored to an extent?

Typical JAR ambiguity it seems...:rolleyes:

Good luck with the rest.
0918

[whydididoit]

I would go with B as well. As a matter of fact, I took that exam today, and thought it was a bit on the tricky side. My room-mate who also took the exam went with A. The problem seems that either answer would work. Oh well....

[silverknapper]

Went with B too, seen it before in feedback and thats what we were told.
Mnd you reckon thats the only one I got right, it was quite tricky!!

[C172Navigator]

I went for B, was in the Bristol feedback.

[Canada Goose]

Mmmmmm.

Yes. Took 8 of the exams this week, and have to say that the Intruments paper totally sucked ! The question you refer to jd was one of the ones that I had less issues with !! Started off on a bad one with Q1/ What is density altitude ...... something I have always known as Pressure altitude corrected for temperature .............. was there an answer option worded to this effect , ....... like b*ggery there was !! A couple of options starting off about pressure altitude and going on about density this and that !! Total nonsense !! Sadly, I fully understand what density altitude is all about and what the implications are ....... however, in the world of JAA, they manage to blur it with wordy gibberish !!

Total f****** nightmare !!

CG
:(