14/7/13: Flight Lesson #5 - Stalling

Got out of bed a bit after 5am this morning for my scheduled 6am flight lesson.  Early!  Had a light breakfast for today's lesson... stalling  :-)  Was still dark when I arrived about 5.50am to the Archerfield airport.  My instructor, David arrived closer to 6am and we got started on the pre-flight theory on stalling.

For those of you not in the know, stalling has nothing to do with the aircraft engine  :-)  Its basically when the wing has reached a critical angle of attack to the relative wind and is no longer able to produce sufficient lift  to maintain level flight.  Lift still actually occurs in a stall although considerably decreased and no, the plane won't suddenly drop to the ground in a stall.  A stall can occur in various flight profiles including in level flight, in a steep turn, in a climb, or in a descent.

Airspeed Indicators have indicators where a stall will occur at particular indicated airspeed in knots (KIAS).

Vs is the stalling speed of an aircraft and indicates its minimum steady flight speed.  Vs is determined by the aircraft manufacturer based on the configuration of Maximum Take Off Weight (MTOW), idle power, wings level, flaps up and most forward Centre of Gravity (CG).

Here's a quick summary of the various airspeeds and ranges as shown on a typical airspeed indicator instrument:

• White arc - flaps extended speed range, ie only extend flaps when operating within speed range of white arc

• Green arc - normal operating speed range

• Yellow arc - caution/smooth air speed range only

• Vso (bottom of white arc) - stall speed in landing configuration, ie gear down with approach flaps.

• Vs1 (bottom of green arc) - stall speed NOT in landing configuration.

• Vfe (top of white arc) - maximum flaps extended airspeed

• Vne (red line) - never exceed this airspeed

Obviously, stall speed changes with various factors including weight and flap extension.

As this was the first flight for the day, before started the pre-flight inspection I removed the wing tie-downs, propeller/cowling covers and the "remove before flight" covers from the pitot tube, static source, fuel tank vents, engine air intake and exhaust.

Due to weather today (scattered showers and fog), we requested a Southern departure to the training area as an Eastern departure would take us straight into low visibility weather.

I radioed:  "Archer Ground, Jabiru 7984, on the Eastern apron with Alpha, dual, for a Southern departure, request taxi"

During run-up checks in the 28R run-up bay, the carb heat check produced about an extra 300RPM indicating my carburettor was iced up!  First flight of the day combined with high humidity (moisture in the air) with a cool air temperature plus low RPM during the taxi from parking to run-up all added up to ice forming around the carb throttle butterfly.  I left the carb heat on until just prior to take-off.

I took off from runway 28R and turned left onto crosswind (with permission from ATC).  I tracked 135 degrees magnetic for the Southern outbound VFR route.  Check out the Youtube clip for this procedure:

http://www.youtube.com/watch?v=oCqAM_9ocek

My stall lessons would be conducted in Class G airspace (uncontrolled) within the training area with Class C lower level steps at 3500ft and 4500ft.  Depending on my position as long as I stay below the Class C airspace steps I won't get any unexpected calls from Brisbane YBBN air traffic control!  :-)

Also in regards to airspace, we had to be mindful and avoid the Amberley military airspace to the West and some Restricted airspace just south of the Class D Archerfield airspace.

To start the stalling exercises, I climbed to an appropriate altitude so recovery could be made by 2500ft.  Then performed the pre-aerobatic checklist (H.A.S.E.L.L):

1. Height - sufficient for recovery by 2500ft
2. Airframe - configured (flap up)
3. Security - no loose objects, hatches & harnesses secure (don't want to fall out during a wing drop!)
4. Engine - pressures and temps ok, carb heat on
5. Location - not over built up areas
6. Lookout - do a 180 degree clearing turn checking for traffic around and underneath us

Without going into fine detail, my instructor demonstrated some power-off stalls which I then replicated.  Key point of stall recovery is NOT TO USE AIELRONS!  Use rudder pedals to correct any wing drop and at same time increase throttle and ease back pressure elevator.  The aim of stall recovery is to do so successfully with minimum altitude loss.

I didn't mind the load factors experienced during the stalls with wing drops, probably because this was intentional and expected.  I actually enjoyed it  :-)  I'm sure it would be quite a different experience if an unexpected stall occurred or worse a significant wing drop! 

Heading back to Archerfield I flew the Western inbound VFR route with Goodna as the inbound VFR reporting point.  Checkout the Youtube clip for this procedure:

http://www.youtube.com/watch?v=ubaKrGPTn-A

We received circuit joining instructions to join downwind 28L.  I joined downwind 28L early at 45 degrees (standard entry procedure) and flew parallel to runway 28L at 1000ft.  ATC advised we could now land on the longer sealed runway 28R so we extended the base leg and came into landing.

I taxied back to the apron and parked.  Great flight lesson and positive comments back from my instructor on my abilities demonstrated both in today's and yesterday's flight lessons.  Plus today I did all the radio transmissions and read-backs ok  :-)

Next weekend is a combined consolidation and introduction to circuits flight lesson.  I'll also be going through some more developed stalls (big wing drops) and be introduced to the circuit procedures... can't wait  :-)