Another Instrument written question....

One of the questions in the FAA exam (I don't have the number in front of me)

Shows a panel where the altimeter and VSI are both still and the Airspeed is very low.
The Attitude indicator looks normal for pitch.


The "Correct" answer is that the pitot system or the airspeed indicator has failed.

Could'nt you get exactly the same indication with a frozen or plugged static line and a climb?

Thought experiment:
1)Plug the static port.
Altimeter and VSI will never ever move again.

2)The Pitot pressure is ambient pressure + impact pressure.
If you climb then the ambient pressure goes down, but the ambient pressure
in the static system stays where it was because of #1 above air speed indicator becomes a backwards altimeter
biased by IAS.


So in insturment flight how would you differentiate from these failures?

Try to do some climbs decents and see if the Altimeter /VSI moves?

Obviously if you have an alternate static source that would be tried early on.


P.S. Closest I ever came to dying in a plane was beacuse of a plugged static port.
I grew up in Alaska, my dad ran a part 135 bush airline.
One summer vacation from college I went for a flight in my Dad's C206T on anphib floats.
I was a bit rusty and way behind the airplane.

The weather was rotten foggy and low clouds. (Like it normally is in South East Alaska.)
There was ZERO wind, and I was making a glassy water landing.
The clouds where low and patchy obscuring the tops of the mountains and creating
an indistinct horizon.

In a Seaplane one of the subtle problems is that if the water is glassy you can't flair, you can not tell how high above the water you are.
On Glassy water you set up an attitude and controlled rate of descent and just wait until you hit the water.

I was trying to land, the VSI made no sense, the weather made visual references difficult and the airspeed
made no sense, The harder I pulled back the faster the airspeed went.
I knew I was in trouble, but I had no idea what to do, nothing made sense.
I will never forget that feeling of knowing you were doing something wrong and not being able to figure out what it was.
I eventually stalled the plane at an altitude of about 10 feet and it just ploped on the the water and stopped.
No damage other than to me ego. IF that had happened 100feet higher I would have killed everyone in the plane.(4 of us)

As I sat there on the water moving about 5mph I looked down and the airspeed was reading 130 knots.
I reached down pulled the alternate static selector and all the gauges went back to normal.

Like most aviation incidents this was a combination of factors
If I was more current I would have had a better feel for the plane.
If the water had not been glassy I would not have had an issue.
If the weather had been better I would not have had an issue.
If the static pott had not clogged I would not have had an issue.
If the plane did not have a STOL kit the Part 135 pilots that flew it regularly would not have "accidently" stuck a twig in the stall warning horn and I would have had warning.

wrote in message ...


Thought experiment:
1)Plug the static port.
Altimeter and VSI will never ever move again.

2)The Pitot pressure is ambient pressure + impact pressure.
If you climb then the ambient pressure goes down, but the ambient pressure
in the static system stays where it was because of #1 above air speed indicator becomes a backwards altimeter
biased by IAS.

This is exactly what happens. Been there done that.

Try to do some climbs decents and see if the Altimeter /VSI moves?

Obviously if you have an alternate static source that would be tried early on.

Pitot heat and alternate static, smash the hobbs meter.

"Ron Natalie" wrote

Pitot heat and alternate static, smash the hobbs meter.

Smash the "Hobbs" meter?????????? :-)

Bob Moore

The key is that the attitude indicator showed level flight. If you had a
frozen static port and were really in a climb, the attitude indicator would
show a climb.

wrote in message
...
One of the questions in the FAA exam (I don't have the number in front of
me)

Shows a panel where the altimeter and VSI are both still and the Airspeed
is very low.
The Attitude indicator looks normal for pitch.


The "Correct" answer is that the pitot system or the airspeed indicator
has failed.

Could'nt you get exactly the same indication with a frozen or plugged
static line and a climb?

Thought experiment:
1)Plug the static port.
Altimeter and VSI will never ever move again.

2)The Pitot pressure is ambient pressure + impact pressure.
If you climb then the ambient pressure goes down, but the ambient pressure
in the static system stays where it was because of #1 above air speed
indicator becomes a backwards altimeter
biased by IAS.


So in insturment flight how would you differentiate from these failures?

Try to do some climbs decents and see if the Altimeter /VSI moves?

Obviously if you have an alternate static source that would be tried early
on.


P.S. Closest I ever came to dying in a plane was beacuse of a plugged
static port.
I grew up in Alaska, my dad ran a part 135 bush airline.
One summer vacation from college I went for a flight in my Dad's C206T on
anphib floats.
I was a bit rusty and way behind the airplane.

The weather was rotten foggy and low clouds. (Like it normally is in South
East Alaska.)
There was ZERO wind, and I was making a glassy water landing.
The clouds where low and patchy obscuring the tops of the mountains and
creating
an indistinct horizon.

In a Seaplane one of the subtle problems is that if the water is glassy
you can't flair, you can not tell how high above the water you are.
On Glassy water you set up an attitude and controlled rate of descent and
just wait until you hit the water.

I was trying to land, the VSI made no sense, the weather made visual
references difficult and the airspeed
made no sense, The harder I pulled back the faster the airspeed went.
I knew I was in trouble, but I had no idea what to do, nothing made sense.
I will never forget that feeling of knowing you were doing something wrong
and not being able to figure out what it was.
I eventually stalled the plane at an altitude of about 10 feet and it just
ploped on the the water and stopped.
No damage other than to me ego. IF that had happened 100feet higher I
would have killed everyone in the plane.(4 of us)

As I sat there on the water moving about 5mph I looked down and the
airspeed was reading 130 knots.
I reached down pulled the alternate static selector and all the gauges
went back to normal.

Like most aviation incidents this was a combination of factors
If I was more current I would have had a better feel for the plane.
If the water had not been glassy I would not have had an issue.
If the weather had been better I would not have had an issue.
If the static pott had not clogged I would not have had an issue.
If the plane did not have a STOL kit the Part 135 pilots that flew it
regularly would not have "accidently" stuck a twig in the stall warning horn
and I would have had warning.

Wouldn't help with the plugged air lines any, but it might get you an
overall lower rental rate - at least till they discovered you smashed the
Hobbs!

"Robert Moore" wrote in message
...
"Ron Natalie" wrote

Pitot heat and alternate static, smash the hobbs meter.

Smash the "Hobbs" meter?????????? :-)

Bob Moore

wrote:

One of the questions in the FAA exam (I don't have the number in front of me)

Shows a panel where the altimeter and VSI are both still and the
Airspeed is very low. The Attitude indicator looks normal for pitch

I assume by "normal for pitch" you mean a level pitch attitude?

I can think of a situation where this could happen which requires
nothing on the airplane to be malfunctioning. Think hard :-)

Rod Machado was his instrument instructor...

"Robert Moore" wrote in message
...
"Ron Natalie" wrote

Pitot heat and alternate static, smash the hobbs meter.

Smash the "Hobbs" meter?????????? :-)

Bob Moore

Instead of smashing anything you would be better off finding out in
advance where your static lines are. On my 182 I have two static ports,
one on each side, but no alternate static system. On the pilots side I
know where the tubing meets the fitting and can reach it while in
flight. You simply yank the tubing off the fitting and now you have
your alternate static source. And when you land there is nothing
expensive to fix.

Ron Natalie wrote:
wrote in message ...


Thought experiment:
1)Plug the static port.
Altimeter and VSI will never ever move again.

2)The Pitot pressure is ambient pressure + impact pressure.
If you climb then the ambient pressure goes down, but the ambient pressure
in the static system stays where it was because of #1 above air speed indicator becomes a backwards altimeter
biased by IAS.


This is exactly what happens. Been there done that.


Try to do some climbs decents and see if the Altimeter /VSI moves?

Obviously if you have an alternate static source that would be tried early on.


Pitot heat and alternate static, smash the hobbs meter.

strong updraft during slow flight?

"Roy Smith" wrote in message
...
wrote:

One of the questions in the FAA exam (I don't have the number in front
of me)

Shows a panel where the altimeter and VSI are both still and the
Airspeed is very low. The Attitude indicator looks normal for pitch

I assume by "normal for pitch" you mean a level pitch attitude?

I can think of a situation where this could happen which requires
nothing on the airplane to be malfunctioning. Think hard :-)

In article 3IGnb.53073$Tr4.118630@attbi_s03,
"Brad Z" wrote:

strong updraft during slow flight?

A good try, but not what I was thinking of.