Lesson 6 - Stalls.

10 July 2011   cancelled due to weather.

17 July 2011   Warrior III - VH-TXH

In 12 years of paragliding I'd never intentional stall my paraglider - probably because it collapses into a ball above your head and all hell breaks loose.  But now I had to make a plane stop flying and fall out of the sky.

My lesson is booked for Sunday 10th July but when I wake up and look out the window and it looks like the weather gods have decided I have to wait another week. My first cancelled lesson. 

Stall by Jetfxer

The next week comes around and the weather is looking much better but when I arrived at the airport, I find out Jason is running very late and won't be able to make my lesson.  I'm starting to think this was not meant to be. 

Luckily Fenella has some time before her first lesson, so I’m not going to get out of it - to be honest I was hanging out for a fly. So once again I’m with a different instructor.  

We take-off and head to the training area and it’s time. 

• HASEL check – Height, Area, Secure, Engine and Lookout,
• Carb heat on, Power to idle,
• Keep pulling back to try and maintain height until,
• The stall alarm starts going off, Carb heat off,
• The buffering starts then plane stops flying and nose drops
• Let it drop, apply full power, keep it straight with the rudder
• As the speed builds level out and return to Straight and level flight.

THAT’S IT??? Clearly I’ve seen too many airshows. While I wasn’t expecting a hammer head stall, I was expecting a bit more of a reaction.

The next few were much the same non-event.  We did have one small wing drop but had it quickly under control with opposite rudder.  All in all, another fun day of flying.

Piper Warrior III VH-TXH,  Flight Time 1.2hr (Total 6.7hrs)

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Technical stuff

•      HASEL check – 

o   Height - 3000Ft+

o   Area – No over build up areas, preferably lots of paddocks,

o   Secure – Hatches, Harness and any loose items away,

o   Engine – Oil Temp & Pressure, Fuel Pressure, fuel pump on, carb heat on, and

o   Lookout 360^O clearing turn, (follow by 90^O turn after each stall)

• For the Warrior III VS₁ (Clean Stall Speed) = 50KIAS and VS₀ (Stall Speed with full flaps) =44KIAS
• The Stall angle of attack doesn’t change.  How the Stall speed does.
• Stall Speed is effected by

1.    Weight – VS₀ and VS₁ are measured at Maximum weight.  The stall speed will be lower when the plane is lighter.
              VS = √(current weight/Maximum weight) X VS_{(max weight)}

2.    Change in wing lift profile Ie Using Flaps, Slats, Damage to the wing, Icing etc.  As an example applying flaps increases the lift produced by the wing for the same angle of attack.  Icing on the other hand decrease the lift produced by the wing.

3.    Dynamic wing loading.  The stall stall increases by 2 main manoeuvres to watch out for  

a.    Turns In a turn the lift vector is banked, so more lift is required counter the weight of the aircraft.  Eg in a 60% bank the load factor is 2.  Increase in stall speed is √load factor ie. √2 =1.414.

b.    Drive recovery. Eg in a 2G pull out the load factor is 2 so once again increase in stall speed is √load factor ie. √2 =1.414.

4.    Use of Power. 

a.    Increasing power increases the airflow over the wing root and hence generates more lift.  It also acts at a lower angle of attack. 

b.    In a climb the power trust line is inclined and the vertical component therefore helps “lift” the plane.

• DON’T use the ailerons to pick up a Drop wing at the point of stall.  Using ailerons to try and level the plane will only increase the angle of attack of the dropped wing further.  This will further stall the dropped wing  making it worst.  Use the rudder instead.  The secondary effect of yawing is roll.
• As the Angle of attack increases the Centre of Pressure C_p moves forward.  At the point of stall it moves rapidly backwards, which causes the nose to drop (Which is a good thing)