[jhb_airlines] Re: Short or Soft field techniques

  • From: "bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Sun, 9 Sep 2007 05:58:05 +0100

You're halfway there.

With no flaps there is less drag and acceleration will be marginally better.
More importantly you have a higher stall speed and so have to lift off at a
higher VR - which means an increased take off run.

With some flaps set you lower the stall speed (as flaps are lift devices)
and so can rotate at a lower speed and use less runway.

Many pilots lock on to the above rule and use flaps for take off all the
time. It becomes so automatic they stop thinking about why they do it - and
get uncomfortable if the habit is questioned. Flaps are good - aren't they?

No. Yes. Partly. Aviation is full of contradictory answers.

In fact flaps are only a good thing up to the point at which you leave the
runway. Once in the air they become a liability as they reduce rate of
climb. Start thinking about this and you can soon see what locations are
better suited to using flaps and what locations would be better leaving them
up.

If you have a short runway or a rough runway then flaps should be strongly
considered. In the first case they get you off the ground quicker and in the
second case they help take the weight off the aircraft so that drag from the
soggy or rough ground on the gear is reduced.

If you have a big hill on the end of the runway it changes your whole
outlook on life. Flaps will get you off the ground further away from the
hill but the reduced climb rate may make the flight very brief. No flaps use
a bit more runway but the climb rate is better and gives you a fighting
chance.

Of course you could end up at an airfield with both a short runway and a
hill at the end (or tree or pylon). Here you can only sit down and work out
the figures for the aircraft by plotting ground run and climb rate with
flaps against ground run and climb rate without them to see which give you
the greater clearance over the obstacle (if any).  Add the usual
temperature, wind and pressure factors plus runway gradient and surface
condition and you may find that on some days it might not be possible at
all. This is where you really should start knowing your aircraft very well
indeed.

In the above I used the phrase "rate of climb" but even here there are two
rules and speeds to learn. Pilots have to know the rate of climb of their
aircraft but also the angle of climb - they are two different beasts (known
as VX and VY)..

Best Rate of Climb Speed is that which gives you the greatest increase in
height over a given TIME period.

Best Angle of Climb Speed is that which gives you the greatest increase in
climb over a given distance.

To stop the mental pressure this may have on some let me simply explain
these by saying the angle of climb speed gives you the greatest gradient
possible but you aren't going up very fast. With Rate you will be higher
after the same amount of time but you will also have travelled further.

Most of the above is just for idle curiosity as FS just isn't up at this
level. In real life you have far more tactile feedback and you can feel the
difference between using flaps or not or climbing at VX or VY. Because FS
gives so little feedback in this respect it doesn't make you question your
technique or your aircraft's behaviour or the weather. You may never change
your landing or take off routine ever - just use the same figures for every
flight. You could never do this in real life and EVERY take off and landing
requires a little thinking about.

Crews on airliners run through an approach briefing for every flight. In
their case it's a review of the STAR, IAP, runway and flap/speed values.
It's not a bad idea to do the same for GA flying in that you could brief
yourself as soon as you pick up the ATIS for the landing point (or tune the
ATIS for a nearby airfield if it has none).

Once you have the wind and declared runway it doesn't take a second to draw
a wind arrow on your map and see the crosswind angle. After checking the
runway length and obstacles you then review your joining procedure, your
approach speed and landing technique. You could also determine your go
around procedure just in case. Thinking up a plan of approach well before
you get to the airfield fills up some of the boring en route time and clears
your head of unwanted thought processes when you finally arrive.

All to often FS pilots tend to fly a portion of a flight and only start
thinking about the next bit as they arrive. It is always better to think
ahead when you have thinking time available so that you get less overloaded
during the more critical stages.

bones

-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Winskill
Sent: 08 September 2007 19:42
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Short or Soft field techniques


Just a quick guess, related to GA. No flap and you'll accelerate more
quickly, to a slightly higher takeoff speed.

With flap the takeoff speed will be, say, 5 knots lower but the
increased flap drag will reduce the aircraft's acceleration.

I've read a couple of GA articles where a short field operator starts
with no flap and drops takeoff flap as he approached Vr.

Gerry Winskill


bones wrote:

>Quite a good article and one I'd recommend everyone reads.
>
>Having done so then I'd ask you all a simple question. What are the
>advantages and disadvantages of using flaps for take off - and using no
>flaps?
>
>Simple question but let's see how much you've learnt after all these
>years using FS.
>
>bones
>
>-----Original Message-----
>From: jhb_airlines-bounce@xxxxxxxxxxxxx
>[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Paul Reynolds
>Sent: 08 September 2007 15:08
>To: JHB List
>Subject: [jhb_airlines] Short or Soft field techniques
>
>
>Rummaging through my bookshelf, I came across a copy of the manual that
>accompanied Papa Tango's Airfiled for FS95/98.  Nothing remarkable
>there. However, opening it I discovered a section on techniques for
>both soft field landing and take offs and short field landing and
>take-offs.
>
>I have scanned the relevant pages and attached them.
>
>Paul
>
>
>
>
>
>
>
>




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