On windshear

[Ramapriya]

1. I more or less know the effects of windshear during landing but how
does it affect an aircraft during takeoff, if at all? Will it induce a
reduced angle of climb?

2. And does windshear show up as a distinct feature in the flight
weather radar?

A link to any site that explains the mechanics of a windshear would be
welcome.

Ramapriya

[Trent Moorehead]

"Ramapriya" > wrote in message
oups.com...
> 1. I more or less know the effects of windshear during landing but how
> does it affect an aircraft during takeoff, if at all? Will it induce a
> reduced angle of climb?

http://oea.larc.nasa.gov/PAIS/Windshear.html

[Orval Fairbairn]

In article . com>,
"Ramapriya" > wrote:

> 1. I more or less know the effects of windshear during landing but how
> does it affect an aircraft during takeoff, if at all? Will it induce a
> reduced angle of climb?

Yes -- windshear will appear as a sudden decrease (or increase) in
airspeed, which manifests itself as reduced (sometimes to negative) ROC.

It takes thrust to overcome a windshear.




> 2. And does windshear show up as a distinct feature in the flight
> weather radar?


No -- radar detects only precipitation or other, solid, objects.



> A link to any site that explains the mechanics of a windshear would be
> welcome.
>
> Ramapriya
>

[569]

Some airports have Low Level Wind Sear Alert Systems, but i've never
seen them work.

[[email protected]]

569 wrote:
> Some airports have Low Level Wind Sear Alert Systems, but i've never
> seen them work.

Most of those systems work by measuring wind direction and velocity
at various points around the airport and comparing them. If there is a
substantial difference between two or more monitoring points, a wind
shear alert is issued.

John Galban=====>N4BQ (PA28-180)

[gatt]

"Ramapriya" > wrote in message

> 1. I more or less know the effects of windshear during landing but how
> does it affect an aircraft during takeoff, if at all? Will it induce a
> reduced angle of climb?

During takeoff an increase in headwind will reduce the distance required for
your aircraft to become airborne and will reduce your groundspeed.

A decrease in headwind will result in a loss in airspeed equal to to the
decrease in wind velocity. Airspeed is fundamental to lift, and lift is
fundamental to takeoff. In practical terms, you wouldn't want to be trying
to clear trees or a bluff from a short field and then suddenly experience a
20 knot shift in airspeed.

I've never seen a weather radar screen so I don't know how windsheer might
be depicted. My guess is it's not; in recent decades they have developed
windsheer detection equipment for that specific purpose, which suggests
there was an inability to do so with conventional weather radar.

-c

[[email protected]]

gatt wrote:
>
> I've never seen a weather radar screen so I don't know how windsheer
might
> be depicted. My guess is it's not; in recent decades they have
developed
> windsheer detection equipment for that specific purpose, which
suggests
> there was an inability to do so with conventional weather radar.
>

Shear can be depicted on the latest Doppler radar systems, but only
if there are water droplets or dust particles in the air. Radar isn't
much help with windshear on a clear, sunny day.
John Galban=====>N4BQ (PA28-180)

[G.R. Patterson III]

Ramapriya wrote:
>
> 1. I more or less know the effects of windshear during landing but how
> does it affect an aircraft during takeoff, if at all? Will it induce a
> reduced angle of climb?

It shows up as a change in airspeed. If the airspeed decreases, the pilot
usually reacts by lowering the nose.

> 2. And does windshear show up as a distinct feature in the flight
> weather radar?

I've been told that windshear can be detected on some types of doppler radar,
and that some airports have this. AFAIK, no radar on an aircraft can detect
windshear.

George Patterson
The desire for safety stands against every great and noble enterprise.

[[email protected]]

Having experienced a windshear encounter just after takeoff, I can
assure you that it is quite hazardous. In my case we both lost 10-15
knots of airspeed and simultaneously were blown a good 200 feet to the
right. I very nearly had to land in the grass. The aircraft was
descending rapidly at full power. I was able to arrest the descent at
perhaps 5-10 feet of altitude, and then gradually regain climbing
flight.

The airport had no windshear warning system.

The tower had warned us of nothing. They seemed quite blase about it
when I reported it, like "Oh, yeah, <<yawn>> that's pretty common over
there on that runway."

Trust not the weather prophets for when the truth is not in them they
will not accompany thee amongst thine ancestors.