[jhb] Re: Pireps
- From: "bones" <bones@xxxxxxx>
- To: <jhb@xxxxxxxxxxxxx>
- Date: Sat, 8 Sep 2007 09:59:43 +0100
30% may sound a lot but it isn't. If the aircraft stalls at 50kts then the
approach at 50 x 1.3 = 65kts isn't that much higher.
For a start it's a reasonable speed to provide stable flying. An aircraft
near the stall is awfully mushy (if it's a good design) and a bad aircraft
can stall one wing without a hint of warning and have you vertical in less
than a second. You can't afford to stall on the approach.
A good margin also allows safe transit through turbulence or mild wind
shear. 15kts is reasonable in bumpy winds near the ground where you can
easily see a 10kt fluctuation in rough air. On really rough days it isn't
uncommon to hear the stall horn bleating a few times on approach.
If ailerons are used too severely near the stall it can precipitate one. The
downgoing aileron actually increases the AoA of that wing and you can
instantly stall a wing by aggressive aileron use at slow speed. This is bad
news because only one wing stalls - the rising aileron on the other side has
reduced AoA of that wing - and it's a prime condition for flicking into a
spin.
As you come over the runway you flare to reduce rate of descent. What you
are actually doing is increasing AoA to provide extra lift and an increasing
AoA produces drag as well as lift. So, from the point you start pulling the
stick back drag will rise and speed will start to decay. This is why you get
into trouble quickly if you pull the stick back just a tad too much and
balloon - speed drops off rapidly and you can easily stall whilst still 5
feet off the ground. Only a hefty bootful of power can recover this
situation - the worst thing you can do is push the nose forward.
bones
-----Original Message-----
From: jhb-bounce@xxxxxxxxxxxxx [mailto:jhb-bounce@xxxxxxxxxxxxx] On Behalf
Of FrankTurley@xxxxxxx
Sent: 08 September 2007 09:20
To: jhb@xxxxxxxxxxxxx
Subject: [jhb] Re: Pireps
In a message dated 08/09/2007 05:52:14 GMT Daylight Time, bones@xxxxxxx
writes:
Approach speed is 1.3 x Stall
Bones,
Why a 30% margin? I can understand why the increased margin when in gusty
conditions, but this seems a lot to bleed off when landing. Or is there a
slowing down phase between approach and landing?
Frank T.
Other related posts:
