OT : Flying a Powered Plane Backwards?!?!

[Azimech]

The Antonov An-2 is famous for being able to do this. Not only that, it's stall characteristics are a real life saver.

[PeterPanPan]

Talking of wind assisted take-offs and landings, you have to see this video of a Twin Otter landing in a very strong head wind. Incredible ...

http://www.youtube.com/watch?v=JwMlg...eature=related

PPanPan

[mazex]

He he, when I was 16 and taking my glider license back in 1986 we had to do a tow from a nearby field where we had been flying on a "camp" for a week even though it was a storm. Both my teacher and the tow pilot where 60+ and had thousands of hours and said it would be good practice for me as an apprentice I have in my logbook with the entry:

1986-07-12, 50 min, Bergfalke 2/55 "Towed from boras in 90 km/h headwind at 700m, tow speed was 135 so it took ages! Landing circuit was performed by reducing speed to 70 km/h and reversing to end of field at 500m. Then fix the shadow at 90 km/h and descend until the ground effect caused a very unpleasant speed drop while still not moving relative to ground. Stick forward to get relative speed and landing with a roll out of maybe 20 meters..."

This was a school flight (my 14:th start) and my teacher who started flying in 1935 told me stories from the finnish winter war where they hovered the biplanes down on lakes in a similar manner. Reduce speed until the shadow does not move and be prepared to apply throttle when the ground effect kicks in...

[RAF74_Winger]

Good stuff Mazek, I assume that by ground effect you mean the transition into the slower moving air close to the ground, is that correct?

W.

[mazex]

Originally Posted by RAF74_Winger

Good stuff Mazek, I assume that by ground effect you mean the transition into the slower moving air close to the ground, is that correct?

W.

Yeah - using english terms I actually mixed it up, what I meant was the wind gradient and not the ground effect (the ground effect beeing the "floatiness" close to the ground produced by the pillow of over pressurized air under the wing and the wind gradient beeing the fact that the wind is a lot weaker close to the ground due to turbulence). The wind gradient is always present in wind and can be quite nasty in strong wind for rookie pilots coming in to slow. Suddenly you can lose 20-30 km/h of air speed while the ground speed remains the same. In this case it was extreme

[AndyJWest]

In the days when I used to fly radio-controlled gliders this effect was very noticable - probably because their airspeed was low compared to a full-sized aircraft. In a strong wind the safest way to land was to push the nose down as you came below about 10-15 ft, and then level off about a foot off the ground to bleed off speed. Trying to maintain a constant airspeed was asking for trouble as you could only do this by diving, which put you into slower air, so you had to dive some more. I should imagine real glider pilots have the same difficulties too.

[mazex]

Originally Posted by AndyJWest

In the days when I used to fly radio-controlled gliders this effect was very noticable - probably because their airspeed was low compared to a full-sized aircraft. In a strong wind the safest way to land was to push the nose down as you came below about 10-15 ft, and then level off about a foot off the ground to bleed off speed. Trying to maintain a constant airspeed was asking for trouble as you could only do this by diving, which put you into slower air, so you had to dive some more. I should imagine real glider pilots have the same difficulties too.

Exactly! And you have to consider it in all aircraft... Big airliners landing at small airfields in strong wind can be seen "losing control" and "fall" the last 10 meters and do a bounce that almost blows the tires. The computers can not calculate the wind gradient as it is dependent on the physical "layout" of the obstacles around the airfield. The proper way of doing it to add x km/h to your approach speed depending on the wind. The problem is if the wind gradient is a lot less present than estimated and the field is small... Then you will have to "battle" the ground effect trying to get you plane on the ground before you run out of airfield. On large air fields major obstacles are therefore cleared from around the runway (for other reasons too ), but some small air fields can have a forest slope on one side. When the wind comes from that direction it gets really bad - we have one field nearby that is like that, many good pilots have bounced both one and two times trying to land in cross wind there.

The problem with gliders is naturally that you cannot smack the throttle if you feel the air speed drop (you always feel it first!) - hopefully you are on full airbrakes and a steep final approach which is the recommended way in heavy wind (just like you did with your rc glider!). If the wind gradient is bad you can retract the airbrakes to get a similar effect like applying throttle. In our Bergfalke case with the 90 km/h wind we approached like a cross in the sky with full air brakes and maximum side slip to have maximized kinetic energy when the wind gradient "stole" the speed. It was still really nasty. The second problem with a glider is naturally if you have added to much speed to counter the wind gradient and the field is small - then your run out of field and you cannot go around for another try

Side slipping was used a lot in old planes with crappy air brakes / flaps. I always use it in IL2 too when landing to be able to do a steeper approach. Works great!

Edit: WWII fighters with minimum forward view used side slipping while landing to be able to see the runway too... Many had bad flaps/airbrakes and in some cases it was the only way. I have flown the Tiger Moth some times and that baby has to be slide slipped at fat angles on final approach as there are no flaps at all... Remember that crossed rudders are a "no no" if the speed is to low - so beware though