Watch Out for the Trees!

[Biggles' Elder Brother - Moderator]

Thought I'd post this about an experience I had today. It turned out to be a near miss - so my Pitts Special gets to fly another day, but I've learnt a number of important lessons from the experience - and so thought I'd share it.

 

It was my first flight of the day, I was flying the Kyosho Pitts Special. For those not familiar a smallish bipe (50" span") with a wing loading like the Forth Bridge!

 

Flying left to right, into wind, I decide, very late in the leg, to do a Split S (or reversal if you prefer - basically a half roll to inverted followed by a half loop). A little 'problemette' becomes quickly apparent. Becuase I've left the decision to do this quite late (bit of an impulse really just because I'd done one at the other end and I sort of thought it looked pretty and two would be even prettier!) By this point I'm very close to the line of trees that marke the righthand boundary of our flying area. Anyway - I decide I have enough room to get the move in and decide to go ahead.

 

[Moral Number 1: don't make last second changes of plan when flying.]

 

I have good speed over the ground and I'm flying into wind so provided I don't go bonkers on the elevator I am a long way from stall territory.

 

[Moral Number 2: don't make rash assumptions about your airspeed!]

 

So over we go into the half roll, let her fly on just a little bit inverted; better, classical, shape to the maneuvre.

 

[Moral Number 3: Pride goeth before a fall!]

 

As I start to pull into the half loop, disaster strikes! Wham a tip stall out of nowhere and I'm inverted! OK, lets worry about the how later - right now its all hands to the pumps to sort this out. I manage to get the nose down vertical, and half roll again then pull out with mega G "elevator stick bending" job. And all is OK.

 

So what the hell happened? Well, those there trees are a very effective windbreak, but you get a lot of turbulance off the top of them and, if the windspeed is just right, you get a lot air rolling down over them - causing a down draft. As;

 

1. I was very close to the trees,

2. there was good breeze blowing,

3. my altitude was just about level with the tops of the trees and

4. the pitts is a failrly small model,

 

I think I got caught in some rather odd, very localised, wind conditions - possibly with a lot of shear. Result - my airspeed, at least for an instant, was not what I might have expected it to be. Suddenly, just as I inverted, a nice steady breeze became a whole bucket full of down draft - and I went down with it!

 

[Final Moral: respect those trees and stay away from them - they have lots of nasty tricks up their sleeves!]

 

BEB

[Former Member]

[This posting has been removed]

[Alan Cantwell]

Had the very same flying a mates 1/4cub at BAE Sarnsbury, wind was blowing off the trees at the rear of the tarmac runway, coming in to land, just pulling in the flair, WAM, dropped out the sky, i was dumbfounded, my mate was not pleased, i had just damaged a blooming CUB, i was puzzled, 10 minutes later, mate was landing his apache aviation sup chippy, same again, 12 foot up, and WAM, now i know why i was warned to be carefull on there!!!

[Lindsay Todd]

We had the same problem at Rednal last year wind shear off the trees like flying into a vacuum, well actually not flying, just falling out the sky, sudden loss of 30 ft has quite an effect on you and the model! Its another case for having visible air!

[Geoff Smith 1]

Ask Chris Bott about windshear. He had the same thing happen at Greenacres when he was maidening my Webbit. If it had been me I would have lost it but Chris's skill saved the day.

Geoff

[Pete B]

A problem shared by many of us! I've got trees on three sides with a wood on a ridge behind the house and the field slopes 10 degrees - the lower field is about 60ft below the landing strip.

My approach from the south is between the trees in the neck of the copse and an approach from the east is a no-no! Anything from a Force 3 up is very challenging.

Mind you, it sharpens the reflexes and makes you a better flier!

Pete

[Alan Cantwell]

is that house yours pete? looks a posh set up

[Tom T]

Looks like a good field though, even with the trees Pete. We had Warbirds day two weekends ago and the trees were removed because of the previous year, the trees acted as magnets.

 

Tom

[wlfk]

In my hang-gliding days, the rule of thumb was that you should leave 7 times the height of the obstruction (trees) in horizontal distance before flying behind an obstacle.

[Pete B]

Posted by Alan 4 on 03/07/2011 08:39:04:
is that house yours pete? looks a posh set up

 

It is mine, Alan but it's better viewed through the wrong end of a pair of binoculars or, as in this case, a screenshot grabbed from a keyfob cam video

 

It was badly built by an English guy (I'd love to meet him.......) and I spent a few years putting it right. Posh, no, comfortable, yes. Great view and very peaceful, but it's not all roses.....apart from being able to step out of the back door and fly !

Pete