ATPL Theory question

[n90bar]

Assuming that the CAS remains constant, if the total pressure probe is blocked, the IAS:

Answer given:

remains constant during level flight, increases during a climb and decreases during a descent.

I would have thought that it would decrease during a climb and increase during a descent?

Any help would be grateful

[littco]

If I remember correctly, when the total pressure is blocked the IAS indicator will act as an Altimeter. Ie Increase in with an increase in height and vice versa.

Because it is blocked the pressure in the total pressure tube remains the same, and as you increase in height the static pressure drops as normal, and so the difference between the pressure in the static tube and the pitot ( IE total pressure tube) will increase , increasing the airspeed indicator. As you descend the pressure in the Static increase and so the difference in pressure between static and total decrease and the the Airspeed indicator shows a decrease.

The key is to remember and airspeed indicator works on the the principle of the difference in pressures between the static and Pitot ( total ) .

[n90bar]

Ah yes, Im with you know, thanks for your help!

[n90bar]

An aeroplane has a stall speed of 100 kt. When the aeroplane is flying a level co-ordinated turn with a load factor of 1.5, the stall speed is:

answer given as 122kts.

Could someone explain this one to me please!

[Kerosine]

Don't take my word for it, Ive not even got my PPL yet, just reading ahead and think i've come across this....

Looking at what you've given

Second stall speed = origional stall speed X root of the load factor?

Dave

[n90bar]

Yeah thats exactly right, I must just be having one of those days!

[littco]

Kerosine is exactly right.

The Sq root of 1.5 is 1.22 when you multiply that by 100 you get 122kts.

As you go into a turn the G force increases this increase has a result the plane increases it's weight. To compensate for this the wings need to produce more lift to keep the plane level, and the stall speed increases.

[Vertolot]

n90bar,

Just refering to your questions about the blocked pitot tube (total pressure probe):

The pressure we get from the pitot tube is total pressure ie. dynamic pressure + static pressure.

We also know that dynamic pressure is proportional(dependent) on the speed of the air (ie. dynamicpressure=air speed), so if we subtract the static pressure from the Total pressure we will get dynamic pressure ie. air speed!

If the Total pressure is blocked and remains the same but the static pressure will decrease when climbing the dynamic pressure (ie. air speed) will increase..