Not another prang!!!!!

[MikeS]

Went down to my club last week and was flying my Cessna 172. Not had this model that long as a brought it off a fellow RCME member. So I decided to do some approaches, landings and togo's.

On my tenth approach I was a little high and carrying a little to much speed so I decided to go around. Set throttle to half and started to climb out. I banked to the right and then it all went wrong. The Cessna seemd to roll on to it's side, I applied left ailreon and right rudder to fight it but it seemd to tip still on the ground nose first.

A few days later I was chatting to another club member about what happerned and he informed me that I had been caught out by the turbulance from the large tree we have and the cross wind coming in front of the tree. It had happened to many other clubs members before.

On the same day I was chatting I was flying my Piper Pawnee with the engine from the Cessna. The wind which was carm had picked up to around 15knots coming across the runway. I made two flights earler in the day with my trusty Pawnee but on the third flight the wind was causing me to crab the Pawnee in to the wind. We get cross winds a lot at our patch so not a real concern.

This time things didnt go to plan. On touching down I brought the nose straight and held the angle until the speed dropped off. But the Pawnee has a large rear fin and small rudder and I could not hold it straight. The wind won the battle, forced the Pawnee round and shattered the plastic wheel hub. The axle caught the ground and spun the Pawnee and it nosed over before coming back down on to its wheels. No other damaged.

[Pete B]

I know how you feel, Mike.

I've had a pretty torrid week or so. First it was the Salto maiden where I had a radio problem and ended up with the port wing in two halves

The following evening, my E-Flite Cub 25 seemed to lose power shortly after take-off and I was able to get her round the circuit and back in safely. Haven't got to the bottom of that yet.....

Midweek, the motor mount of my venerable and well-beaten E-Flite Sea Fury decided to part company with the foam fuselage, once again....should have put it down into the long grass, not the close-mown runway!

Terry Walters came up for a days flying last Friday. I was rather hoping my luck would change - it did - but for the worse! He was the one who went home with everything intact - for a change

My VMAR Fournier caught a wingtip on the long grass at the edge of my narrow runway at take-off. Knocked out the front end of the motor mount and side-swiped the rudder. Fortunately my Gorilla Glue arrived from the UK the same day (cheers, Terry!), so all is now fixed

The Druine Akrobat then ran off-piste into the long grass and, despite there being no damage, the ESC decided that it no longer wanted to control the motor, so that has been replaced today. I've taken the opportunity to change the battery access to save having to remove the wings each time.

Finally, my beloved CG Cub had a very lucky escape when I screwed-up a crosswind take-off and it went into the long grass at a fair lick. I'm still wondering how I got away with a bent u/c leg and a couple of minor puncture wounds..........

A couple of nice flights with the Phoenix Rainbow did go some way to restoring my confidence, though......

The rush of nothing to the head continues today, though. Fixing up the Akrobat, I managed to solder an XT60 connector the wrong way round - and only noticed when the pack was connected and started to swell and get very hot indeed.......

First time I've done that and kicking myself for it. Anyway, the pack - and it's one of my newest Nano 4S's, naturally - seesms to be benefitting from a balance charge as I type, phew!......

I think I'm going to have to start listening to myself when I start thinking, "Today isn't a good day".....and find something else to do!

Must get back to fixing..........

Pete

ps...........and, as a result of the polarity mix-up, I've now fried a perfectly good 50A ESC.....Aaarrgghh

 

Edited By Pete B on 07/06/2012 21:59:33

[Biggles' Elder Brother - Moderator]

Hi Mike,

troubles definitely come in gangs don't they! Sorry to hear about all this - at least the Pawnie isn't too badly damaged.

Obviously I didn't see what happened to the Cessna but your excellent and detailled description suggests an alternative explanation. When doing an overshoot I always think its best to be really decisive about it - no half measures. Full throttle, give it good opportunity to regain flying speed level then ease back to climb out. Delay any turn until you are really sure you have a fully flying aeroplane again.

The problem if you only go half throttle is that speed pick up will be very slow, and because psychologically you've prepared yourself for a landing your perception of speed can be a bit unreliable. If you then pull up to soon, you're now slow and at a high angle of attack - this is real stall territory!

Now add a turn into the mix - in which part of the wing's lift is transferred into side thrust to turn the model, so you pull a bit more elevator - and bang! Straight into a stall - but one wing stalls first (most probably the oneon the inner side of the turn as its got a lower airspeed) and what results is exactly the sort of "spin-in" that you describe.

We tend to panic a bit now and when we panic (and the ground is approaching fast) what do we do? We pull yet more elevator! That just increases the angle of attack even more and pushes us ever further into the stall and we watch helplessly as our pride and joy "falls/spirals out the sky".

Have a think about it - could this have been what happened?

BEB

[Martin Harris - Moderator]

It's weird, but I've had several pupils who seem reluctant to apply full throttle on an overshoot. They often try to start the climb out before thinking about opening the throttle.

Which makes part of my anatomy twitch every time!

In a critical situation (i.e. within easy reach of the hard green bit) energy is king. Turning that energy into height is often a short term gain for long term pain. I don't care about height (hedges permitting) if I haven't got an adequate margin of airspeed to maintain positive control - in a worst case scenario the model hasn't got so far to fall...and a glancing blow to Mother Earth is preferable to a full scale thump from height. So the thing to do is to make sure that some of that lovely potential energy in the fuel tank or battery is converted to its kinetic form - then you can worry about getting enough height for the next circuit and attempt at an approach.

One other thing - you stated that you applied the Cessna's left aileron and right rudder. From the description, you were trying to pick up the right wing (most peoples instinctive reaction).  These actions would have made the situation very much worse as this is a classic spin entry configuration. Many full size gliders are reluctant to spin UNLESS you apply out-spin aileron, for example.

Using aileron to pick up a dropping wing increases it's angle of attack and would lead to an even more rapid wing drop...couple that with in-spin rudder and there's going to be a new hole in the ground!

Edited By Martin Harris on 08/06/2012 00:23:51

[David Ashby - Moderator]

Mike - sorry to see that. As Dave says, at least the Pawnee looks fixable?

Pete - you've been having some fun there! 

 

Just to throw something into the mix chaps but chatting to large warbird pilots

(large models that is...) ; they have told me that some models need a graduated application of throttle after an abort landing decision just to avoid a torque reaction - some warbirds will react violently and roll into the ground after having the throttle banged open at the end of a slow pass.

Appreciate a Cessna isn't a warbird of course.....

I've been taking evening classes in 'how to start an aerodynamice debate'

 

 

Edited By David Ashby on 08/06/2012 08:54:32

[Martin Harris - Moderator]

On top of which, whacking the throttle open on a glow, particularly after a spell of idling such as on a highish approach can sometimes lead to a deadstick.

The Sopwith Camel was the classic in this respect - countless pilots were lost due to the incredible gyroscopic and torque reactions from the heavy rotary engine and prop, coupled with the rudimentary throttles (and with no throttle at all on some engines fitted, where power control was simply by switching ignition on and off on various cylinders). At a slow airspeed there was simply insufficient control authority to do anything to counter the roll and yaw produced by rapid engine accelleration. As power outputs went up in WW2 it started to become a problem with more modern engine layouts as well.

[Biggles' Elder Brother - Moderator]

I'd agree totally. Slamming the throttle open on any model with a fair excess of power could easily provoke a torque roll and its "goodnight Vennia". What I do try to tell folks is be decisive - not half hearted - open up all the way, keep it level until you're sure its out of the danger zone.

I also agree with Martin - beginners often do seem to have a marked reluctance to open up decisively at this critical time. I don't know why. Over the years I've come to the conclusion that lack of commitment to a particular course of action (dithering in my case!) causes a lot of crashs. If you decide the "throw away" a landing you're in a potentially dangerous situation - low and slow, it needs a firm decision - either you're going to go ahead and land - maybe long - or you're going round again. Getting caught in the middle is the worst of all worlds.

BEB

[Cyclicscooby]

Sorry to hear about ALL your woe's...

Hope you get it all fixed soon.. Both of you..

Can't say I suffer with power issues, with my profile hack, and side winds are just normal, but I have noticed the hedges cause massive un-seen turbulance if the winds blowing a cetain way.. Quite un-predictable too, as above, your slowing down, 15ft up, balancing a tipping wing, then whoa.. it wobbles everywhere for no reason.. If you haven't the power or agility to sort it out, it'd be fatal..

Best of..

Luv

Chrisie.. xx

[MikeS]

I agree with all of you. The cessna with the 46Ax at half throttle moves like a scalded cat. No worries when it comes to speed. On my overshoot I was happy I had enough speed and lift before turning. The Cessna comes in at around 5lbs auw. As with crashes like this I always follow the evidence.

I do feel that it was pilot error though. I have ruled out any problems with the Cessna before the crash. Everything is in working order, servos all work apart from elevator which was stripped in the crash.

I have a DX7 and use AR7000 rx. I run a Lipo as my flight pack using a bec to power the RX and servos.

I checked the DX7 with the Pawnee before the flight and as always do a range check. I checked for fades, loses and volts (5.9v) with the AR7000 and all was good. No issues during the following flights with the Pawnee and my Pulse XT.

So it seems it was Pilot error which I would rather be the case. Thinking back to the day and reading through everyones points I have to agree I stuffed up and crashed the Cessna. BEB's suggestion of what might have happerned seems to be almost be like he saw it him self.

I think have learned a lesson here.