CPL AGK questions

[UnderneathTheRadar]

Hi all,

Still scratching my head from 2 very odd blocked pitot/static line questions encountered this afternoon.

Can anyone tell me the answers to the following (and why):

1. A pilot is passing 3500' on climb to 9000' on an a/c with separate pitot and static systems when the pitot becomes blocked. The pilot will notice which of the following effects:
a) VSI and altimeter return to 0
b) higher nose attitude required to maintain climb IAS
c) none
d) lower nose attitude required to maintain climb IAS
e) VSI remains at last value

(a & e may not be exactly right but were options involving the static system).

2. A pilot is commencing a climb to cruise altitude when the pitot system becomes blocked. The weather at the destination is marginal and the pilot wishes to calculate the PNR. They should be aware that:
a) the TAS will be higher than indicated
b) the TAS will be unchanged from that calculated from IAS
c) the TAS will be lower than indicated


Any help gratefully recieved.

UTR.

[PAPI-74]

All you need to remember is PUD SOD
Pitot blocked=under read in descent
Static blocked=over read in descent and visa versa

1/
pitot blocked in climb
PUD=over read in climb
if it over reads you will want to climb at a higher angle to keep the speed back (dangerous as you will stall)
b is the only answer

Try to get rid of the wrong ones.

2/
another PUD
you are at a higher altitude that when the blockage occured so it will over read. You will slow to your cruise speed and end up slower than your VMD and will loose range.
Because you have slowed down, the TAS is lower
c is the answer

I hope.

Just think of these q's as a game between you and a sick individual, trying to trap you. Don't get frustrated, just look into the question and read it a few times to avoid the wrong drift.:ok:

[PAPI-74]

As to why, draw yourself a diagram and this will always sort you out.
How are your text books at explaining it?

[PAPI-74]

Good piont. It's been a while, so I am off to revise again. Be back in a moment.

[PAPI-74]

DirectAnywhere is right. God I have gone rusty.
If the pitot becomes blocked from ice, lets say, it acts like a barometer, reading changes in static pressure.
It would give an inc in speed as the a/c climbs (the speed is now altitude)

Dynamic press is removed
Static pressure is sealed in the pitot and bellows
Static in the vent is variable so all it can now read is altitude in effect.

c is correct as DCT has mentioned.

[UnderneathTheRadar]

Thanks all.

Yes, they are CASA questions from the exam.

PAPI-74/DA - for question 1 agreed with your logic at the time however the question specifically asked for the effects which would be noticed by the pilot. I reasoned that pulling back on the nose would have no effect - with a blocked pitot, no matter what you did to the angle of climb there would be no effect on the IAS hence option B is not possible.

For question 2, yes, they specifically mentioned IAS and I was stuck with the conundrum of trying to work out if TAS was the actual speed of the aircraft thorough the air (which I thought it should be but then the answers don't work) or if TAS was some theoretical number calculated from the climbing IAS which would be completely different to a cruise IAS (which do make the answers fit). Using this assumption, I agree that the answer was c.

Anyone think these questions are worth challenging? I passed fine anyway but they are specatcularly bad questions.

UTR.

[Shitsu_Tonka]

Reminds me of the ATPL exams I did (twice!) in 1996. Not at all a test of knowledge, but a test of word games and totally stupid interpretations rather than the fundamental of the problem at hand.

If you were flying in a multi crew cockpit and had this type of problem, and one of the crew asked how this would affect the PNR I imagine you would send him/her out to unblock the pitot!

Fortunately I got through by just doing what was suggested above - consider it an artificial hurdle thought up by some sicko sitting in a windowless box in Canberra, and work out what the 'most correct' answer could be.

[Arm out the window]

Drawing a diagram like this one is always good - you may already be doing this:
http://i109.photobucket.com/albums/n52/tborella/ASI-Diagram.jpg
For Q1, the chamber fed by the blocked pitot tube is now sealed. In level flight, the IAS reading would stay constant no matter what actual speed he flew at. In a climb, the static pressure into the other side will reduce, causing an apparent increase in IAS.
However, nothing he does with the attitude is going to affect the IAS indication, so the question, as noted by others, is a sadly ambiguous and confusing one.

If I had to choose, I'd say b would be the go, as a and e are out, he'd be Blind Freddy if it was c, and as it's overreading, his reaction is hopefully to raise the nose. What a poor question.

Q2: Again a bad one, as a number of interpretations could be had. However, blocked pitot, static pressure reduces as he climbs, so the ASI overreads assuming all other things being equal (a big assumption!). As the question says 'indicated' instead of IAS, I'm assuming they're talking about the TAS he calculates from the indication, which would be higher than it should be. So I'd go for answer c.

[UnderneathTheRadar]

Yep, no problems with the theory - just with questions that make no sense and have no sensible answers.

UTR

[Arm out the window]

What answers did you pick for the exam?

[UnderneathTheRadar]

In the exam I picked "no change" for the first question as the pilot could not have seen any of those effects.
For the second, I picked TAS is higher than indicated as contrary to PAPI-74s reply, I make it that TAS should increase in the cruise which also means a higher IAS than indicated. I think I probably, incorrectly(?), reasoned that the change in density altitude which caused the IAS to read higher than it was would be more than offset by the change in TAS induced by the switch to cruise.
In both cases I should probably have gone with the 'least incorrect' answer and used the KISS principle though :(
Thanks for the feedback, I've emailed CASA with my opinions and will see if they reply.
UTR.