Failure of something!
|Paul C.||25/01/2019 10:06:52|
609 forum posts
The up side of loosing a model is that there is now room in the workshop for a replacement , I built another of Peters models Little Miss Honky Tonk . As they say , every cloud 😃
|Piers Bowlan||25/01/2019 10:23:11|
1954 forum posts
It is good to be philosophical with this hobby! LMHT, wow, that was quick Paul, we only got the plan last week! Did you use the same engine or do a leccy conversion?
|Paul C.||25/01/2019 10:56:03|
609 forum posts
Not that quick Piers I had a pdf copy from Peter before the mag came out, yes it's the same ASP 52 engine . Needed a new cylinder head from just engines as the rocker cover bolt cracked the thread in the head, did not want to risk it so I replaced. You are absolutely right about having to be philosophical , in my youth I used to fly control line combat those models had a very short but eventful life
|Sam Longley||16/07/2019 18:47:27|
|75 forum posts|
A possible tip for those, like me, that seem to get attracted to trees is to have a cheap fishing pole in the kit. Mine is 9 metres long when extended & is quite stiff. Folded it is about 800mm long. I have a nice stainless steel wire prong taped to the top made from a wall tie. Mine was purchased whilst on holiday in France & cost 22 euros from a French fishing tackle shop. 9 metres along with my height gives one a considerable reach & i often do not need every section.
Seems to get borrowed at regular intervals at the club & at our yacht club as it is also good for catching stray lines up the mast.
|Sam Longley||16/07/2019 18:50:43|
|75 forum posts||
I suppose it would be too much of a thread drift to ask for you to elucidate a bit more on that one
|Denis Watkins||16/07/2019 19:00:50|
|4007 forum posts|
Trees effect full-size too
|Peter Jenkins||16/07/2019 23:53:09|
|1317 forum posts|
The infamous stall on the downwind leg is caused by pilots thinking that a high downwind ground speed can be reduced by reducing airspeed! The result, is the infamous stall on the downwind leg.
It is quire surprising how many experienced pilots, and even an examiner on one occasion, do not understand the vital difference between air speed and ground speed.
An earlier comment by Simon Cragg falls into that category.
Where things do get confused is when you are descending through a wind gradient (that is wind speed reducing as you approach the ground - exactly like the boundary layer on the wing). In this case, you need to increase your approach speed when landing otherwise as you descend your airspeed will drop away as the speed of the block of air reduces. That is unless you have a very light foamy that immediately reacts to the change in airspeed.
Aerodynamics is not something most model pilots have studied. Where they have it tends to be at a very basic level. Some of us who post on here actually have studied aerodynamics to degree level, have done flight test courses and flew full size power and gliders. It's up to you if you wish to ignore the advice but don't complain when you end up with a broken aeroplane because you ignored the advice.
|J D 8||17/07/2019 08:22:03|
1341 forum posts
When I was learning to fly gliders [ full size ] in the 70's one of the instructors had a very annoying habit. You would be on finals about to turn in to land when if the aircraft felt the bump of a thermal [ coming off a large area tarmac at the edge of the old airfield ] He would snatch the controls catch the lift and up you would go to start again. It was hard to learn anything with him.
One day though he did not catch the lift and had to drag it in over the fence as he had done before. However a new large road sign had been erected on the road around the field. As he passed over the sign about 20 foot up the old T21 Quit and dropped to the ground with a hell bang ripping the tail off on the boundary fence. I was not the pupil on this occasion I am glad to say.
882 forum posts
Peter has answered your question for me and almost certainly made a better job of it too.
|OZ e flyer||17/07/2019 11:36:20|
144 forum posts
Stall on downwind leg. Grumman Mallard. January 2017.
unfortunately 2 people tragically lost their lives. This happened in front of thousands of people setting up for our “Australia Day” celebrations.
|Martin Harris||17/07/2019 14:14:18|
9035 forum posts
Too slow and dropped a wing off the stall - look at the nose high attitude during the turn and the result would have been the same whichever direction he was travelling in. (Technically speed is not the whole story - a wing stalls at a critical angle of attack and this can happen at very high airspeeds, but in normal flight regimes is a good guide in most circumstances). If there was a strong wind it's possible that the proximity of the surface during the low turn may have deceived the pilot by making the apparent speed higher than his airspeed.
I wonder if the pilot realised he was too slow and opened the throttles - the sound heard could have been that of only one engine responding and could have exacerbated the situation. Difficult to assess when the throttles were opened at that range though.
Edited By Martin Harris on 17/07/2019 14:15:06
|Sam Longley||18/07/2019 09:08:23|
|75 forum posts||
Thanks for posting that & I asked because as a yachtsman (My main hobby so I tend to get out of practice each year) I am aware of speed over ground & speed through the water caused by tidal drift. I expected the same for an RC plane in the wind
In training for my A test the instructor spent a lot of time teaching me throttle control & would get me to reduce throttle on down wind legs. I could never understand why, because if a model needs 30 mph to fly then if the wind was 10 mph it would do 20 mph up wind & need 40 mph down wind. Hence dropping back to 30 mph down wind always seemed wrong.
We had a senior examiner from the BMFA come to the club to talk about work of the BMFA & flying demonstrations were given to show various aspects of testing. He also mentioned reducing throttle on down wind legs. I was too nervous to challenge his comment at the time, as he was a senior examiner & I had not yet passed the A test. (I have now)
However. I have had several stalls & the inevitable spins just as I have turned at the downwind leg (did not happen with trainers, so problem never arose) & you really have shown me that I must try to forget the habit that I got into in my learning & make sure I open the throttle a lot quicker before starting the turn.
Thank you & sorry for the thread drift
Edited By Sam Longley on 18/07/2019 09:11:10
|Bob Cotsford||18/07/2019 10:36:59|
8133 forum posts
It's fine to reduce the throttle on the downwind leg, just don't try to maintain the same rate of climb or maintain altitude (depending how much you reduce throttle). When learning to fly it's very easy to get too far downwind and then have to fight to get back to the field with the extra difficulty of flying towards yourself while panic levels are starting to ramp up. Hence reduce throttle to slow downwind progress and give yourself more time to plan your turn at the end of the downwind leg.
|Martin Harris||18/07/2019 10:53:34|
9035 forum posts
Personally, I would avoid even the suggestion of throttling back in the circuit unless you wanted to reduce the rate of climb or altitude.
If the wind is strong and you want more time in the downwind leg, extend the into wind portion and correctly offset the headings in any crosswind legs to avoid drift.
Bad habits are easy to learn but persist with getting the basics right and it will reward pilots over many years for their efforts. Correct use of throttle and elevator on the approach is a skill that often goes unlearnt resulting in close calls and model damage time after time.
I'm a little shocked (but not totally surprised) that your senior examiner should have advocated the practice of throttling back downwind - hopefully something did not come across as intended but there are many experienced model flyers who could usefully learn some more basic aerodynamics.
|Peter Jenkins||18/07/2019 12:24:36|
|1317 forum posts|
I heartily concur with Martin Harris. All I would add is that if you need to commence your descent on the downwind leg then reducing the throttle in order to commence the descent is fine. Many pilots tend to close the throttle completely and just use the elevator until they land. Unless you are high, this is poor practice as the elevator controls speed and throttle controls height. Too high an approach speed will mean the aircraft will float a long way and may still have flying speed at the end of the strip. Too low a flying speed and you run the danger of stalling. Practice the right speed at a safe height - generally speaking a shallow descent with 1/4 throttle is good. If you are in danger of undershooting add sufficient power to flatten the flight path so you can reach tge strip and then return to 1/4 throttle or less. Maintain the attitude of the aircraft with the elevator so speed remains constant. As you begin the round out close the throttle. It is worth spending time on getting landing in the right place at the right speed right as it helps to reduce damage. Always overshoot if things start to go wrong and have another attempt.
|Peter Christy||18/07/2019 12:28:41|
|1650 forum posts|
I was always taught to control speed with the elevator and height with the throttle. There may be exceptions during aerobatics, but it works very well in circuit flying!
|Martin Harris||18/07/2019 12:48:41|
9035 forum posts
Thanks Peter for correcting my laziness and expanding on my points to perfection! There is little more satisfying in model flying than setting up a scale approach and watching the immediate glideslope corrections resulting from throttle movement. The only elevator movements needed are fine compensatory ones for the throttle changes or more robust inputs for gust effects until the flare commences.
Pete - I suspect your full size experience contributes to your understanding?
|J D 8||18/07/2019 17:55:21|
1341 forum posts
One feature of model flying I have never been keen on which is often taught is the square circuit / approach, downwind leg, 90 degree turn onto base leg, 90 degree turn onto final approach.
Usually fine with trainer and lightly loaded types but when pilots move on to more advanced types the extra gee in those turns can provoke a stall more so if the downwind turn problem is factored in.
I prefer a more oval descending turn starting at the end of the downwind leg.
|Peter Christy||18/07/2019 18:20:16|
|1650 forum posts||
Well, my full size experience is well out of date! I did go up for an hour long air experience flight at Dunkeswell in 2017, to celebrate the 50th anniversary of my first solo! I was doing quite well until we got on to steep turns, which is when I realised that my stomach isn't as strong as it was 50 years ago!
JD8: The oval descending turn - otherwise known as the "fighter break", favoured by Spitfire and Hurricane pilots during the war as they couldn't see the runway over the engines during a straight approach!
And yes, it can make judging the approach a little easier, as it can be stretched or shortened by adjusting the turn.
|Peter Jenkins||18/07/2019 19:12:48|
|1317 forum posts|
JD8, I cannot agree that flying a square circuit with a non trainer is any more likely to provoke a stall. Provided you keep your bank angle to not more than 45 deg and you can also add a whiff of power, as we were taught in full size, you are quite safe. I fly both types and have never experienced a stall in the turn - to date at any rate! Provided you are following a descending path and have a good idea of what your aircraft feels like as she gets slow you should not have any difficulty, If you do, then the answer is to practice some more and not shy away from a standard manoeuvre. Why else would the requirement exist for a rectangular circuit if it were more dangerous. I think this is another myth that needs to be challenged.
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