Peter Jenkins

February 3

I was told to upload video to YouTube and then post the link on this forum.

February 3

4 hours ago, Futura57 said:

Hello Peter, please clarify the above extract from your post. Two questions immediately come to my mind. But maybe I misunderstand.

1 - If the down force on the tailplane increases, won't this push down the tail and thus raise the nose i.e. pitch up ?

2 - You refer to incidence, but do you mean angle of attack? The former is fixed by the geometry of the aircraft design. The latter is a variable of flight?

Hi Futura

You are quite right for pointing out my error! I have now drawn myself a diagram, reproduced below that shows what I was trying to say and got round the wrong way when I put it into words!

In the normal stable position, i.e. the CG is in front of the centre of pressure - the point through which the wing lift acts - that will leave a nose down pitching moment as shown in the diagram. This is counterbalanced by the tail plane down force.

As power is increased and now exceeds the drag force, the wing lift increases and the nose down pitching moment also increases and thus acts as the restoring force to act against the down force provided by the tail plane. The increase in airspeed will also result in an increase the the tail plane down force but this is not of the same magnitude as the wing lift generated force. Thus the nose down pitching moment increases and tends to restore the equilibrium between that force and the tail plane down force.

If you move the CG further and further aft, this nose down moment reduces thus reducing the stability of the aircraft. If the CG coincides with centre of lift then there will be no nose down pitching moment so the aircraft will be neutral in stability. Move the CG behind the centre of pressure and the moment acts such that the aircraft is now unstable and requires the pilot to alter the tail plane down force to counter the pitch up or down by the aircraft.

I was also loose in using angle of incidence when I should have said the angle of attack. The angle of incidence, as you point out, is fixed by the relationship between the wing and the fuselage when they are joined together. The angle of attack refers to the angle between the wing and the oncoming air flow. The angle of incidence will set the sit of the aircraft at a chosen speed.

As an example, airliners are designed to have the cabin floor level at their designed cruise speed. When the airlines wanted to save fuel burn they reduced the cruise speed and then the aircraft had to be flown with the wing at a higher angle of attack to generate the same lift but at a lower speed. Thus, the cabin crew now had a downward slope to the cabin floor when going towards the rear and an upward slope when going towards the front of the aircraft making life a little more difficult for them. Had the airliner had a wing whose incidence could be adjusted to allow for this then the cabin floor could have been returned to being flat at the lower cruise speed.

One of the reasons for using a canard layout for a fighter is that when turning at say 9 g all the lift generated by both the wing and the tail plane is working in the same direction as the canard now provides an upward lift force to balance that nose down pitching moment.

Finally,

The difference between the thrust line and the centre of drag i,e, the point through which all the drag force components operate through, also will produce a nose up or nose down pitching moment when power is applied or reduced. If the thrust line passes through the centre of drag then there will be no such moment generated. That's the aim of up and down thrust adjustment. You can have zero moment and thus application or reduction of power will have no instantaneous effect or accept the mismatch and have either a pitch up or pitch down with power changes. Once the power change has resulted in an actual airspeed change then the wing lift is affected and my earlier comments apply.

Sorry for not saying what I meant first time round! Smack on hand adminstered!

February 3

1 hour ago, Dai Fledermaus said:

Good to see Ireland win the Grand Slam this evening. 😊

Brave prediction!

February 3

Hi Simon, sorry, have to take issue with you in your post above. I agree that applying power from a set trimmed speed will cause the aircraft to accelerate until such time as the the increase in drag force now equals the additional thrust force. The increased air speed will generate more lift and that's what makes the aircraft climb not natural stability but more lift will also increased induced drag adding to the profile drag caused by increased speed. The natural stability will act to try to achieve a new balance of forces. The increase in air speed will also increase the downforce generated by the tail plane (it is always a down force in a stable aircraft) and that will tend to reduce the wing's incidence and hence lift and thus counter the climb until a new state of equilibrium of forces is achieved but in this case with the aircraft climbing.

With model aircraft, we have hugely more power than most light aircraft has so the effect of a sudden power increase is much worse for a model aircraft. You can make an aircraft very stable such that the stability forces are moderately powerful e.g. a forward CG. Moving the CG aft, will then reduce the power of the aircraft's stability.

For Free Flight aircraft, you want high stability as there is no way of controlling it once it is released so it's stability is all that will keep it flying safely. These aircraft are generally designed to fly at the lowest sinking speed once power has been lost and will be trimmed to climb relatively steeply under power to gain the required height before the engine cuts or the rubber band has exhausted its power and so have a relatively high wing incidence to allow the fuselage to not be too tail down. You want the fuselage to produce the least amount of drag from both form drag and skin friction. Having the fuselage level with the airflow as the aircraft descends, reduces the fuselage's form drag to the minimum. Using such a model for flying the aircraft as a radio controlled as opposed to guided aircraft means you have to re think the basic aircraft set up.

Stability remains important but response to controls is also important. Many have flown models with the CG set too far forward and find them unpleasant to fly. With the CG in the optimum position, while stability will remain positive it will not be as powerful in the case of a free flight model. The issue David was seeking to fix was that the application of power above a certain minimum caused the aircraft to climb markedly. The solution is to reduce the wing incidence so that the aircraft can be flown at a greater range of engine power without the controls being overwhelmed by having to apply full down elevator to hold the aircraft level.

Positioning the CG is one of the most powerful trimming tools available to us but many pilots are unaware of this fact. All aircraft will have a range of CG where with a forward CG you could reach the point where on a tricycle undercarriage aircraft you have to apply almost full up elevator to get off the ground. This makes rounding out for landing very difficult if not impossible and you either need to have more elevator movement or move the CG a bit further aft. Of course, you get to a point where the CG leaves the aircraft neutrally stable which means it will not correct itself if you disturb it and if the CG is moved further aft then the aircraft becomes unstable - not grossly so just that if the aircraft is pitched up by turbulence it will continue to diverge by pitching more and more until the pilot applies down elevator to stop this and return to level flight at which point the aircraft will have to be flown all the time as it has negative stability.

Getting the wing incidence, down thrust, CG and control throws sorted out can make an aircraft a delight to fly from one that is very disappointing.

February 3

Thanks for posting the video Jolly Roger. Took me back to the days I flew a K6e with the Army Gliding Club at RAF Odiham where I was stationed. It was lovely to fly but the one thing I learned not to do was to let go of the stick!

I was hunting around for my sarnies that had slipped to the rear of the cockpit. I needed both hands free to do this. There was a slight bump as I flew through a thermal and then all hell broke loose! The tailplane was all flying and quite a light construction while the stick was curved back towards the pilot is a shallow S. The lack of damping in this set up allowed the stick to be thrown fully aft then fully forward rapidly! My head hit the canopy 3 times before I waa able to catch the stick and stop these violent switchbacks! After that experience, I always clampedmy knees around the stick if I needed both hands free!

February 2

38 minutes ago, Ron Gray said:

And WeeWee has left his seat!

That's the other wonderful thing about this dark coloured waterproof clothing! 🙄 Gives you a warm feeling......

February 1

1 hour ago, Tosh McCaber said:

Any more details on the suits guys?

Mine was from Dickies but they don't seem to be importing them any more. Just Google for one piece cold weather suits.

February 1

6 minutes ago, GrumpyGnome said:

I learnt I need a warmer coat.....!

Ever since I bought a one piece wind and waterproof padded suit and a warm helmet type hat with a chin strap to do up snug, I find that I can stand conditions that would have put me off before. Well worth the £55 it cost to buy the thing. Oh, and a pair of Zippy hand warmers.

February 1

1 hour ago, PatMc said:

Don't bother messing with the downthrust & definitely don't faff with the wing incidence, you only need to reduce the available power to a suitable level. Just try fitting a lower pitch, smaller dia. prop. You will have to experiment with a few to see what works best. For preference try ones designed for ic.

Some F/F people even used to fit the prop on back to front as a make do temporary field fix.

On what basis do you make your statement about not bothering with adjusting wing incidence please?

February 1

Look like it's got a Tallboy in the bomb bay Leccy!

February 1

David

Reduce the wing incidence by packing at the rear as we used to do in the old days. Keep reducing the wing incidence until you can apply power without the model pitching up immediately. Down thrust and wing incidence are sort of interchangeable adjustments. Your problem isn't the power it's the mismatch between the wing incidence and the thrust line.

I know it's very far from an aerobatic model, but that's what we do to reduce the effect of power on the aircraft's attitude. You will find that it will be fine with the old spec motor if you dial down the incidence till the application of power has no effect on the aircraft's immediate attitude. As the model speeds up with more power, it will climb as the lift increases but not nearly as violently as you describe. Equally if you close the throttle it will not dive suddenly. You will be pleasantly surprised at what reducing the wing incidence will do to overcome your problem. Indeed, it will just go away!

February 1

A lovely day in Suffolk but sadly, I was the only one there this morning! Forgot to take a photo so you'll just have to image a blue sky and sun and about 10 mph at 40 degrees to the runway I was using. Got in a bit of cross wind landing practice.

January 31

1 hour ago, Barnstormer 52 said:

My grump is with the BBC

Why not include a picture of the actual drone used in the offence, rather than something that resembles 'The Flying Bedstead'.

Why use the term 'Hobbyists' - which seems to infer the blame lies partly with other model flyers, knitting is a hobby as is restoring vintage cars.

'Other hobbyists' sems to me to imply that he is involved in model flying - if he was then surely he would have known he was in the wrong.

I regularly make spelling mistakes but you would think the BBC would proof read what they write - offence 3 is listed as

Alternated the drone controller to allow the drone to fly further distances, contrary to the Wireless Telegraphy Act 2006

You, and all the rest of us, can complain to the BBC about their failure to report without bias. Use this link. It's all fairly simple to do. So, if the BBC gets a load of complaints on this article they might, might mind you, do better in future! Given their well publicised bias in a lot of other higher profile news I doubt it will change the way they do things but it just might.! I shall be filling out that form shortly!

January 31

Report on the BBC website.

January 30

1 hour ago, Jolly Roger said:

I really enjoy having challenges in my modelling, but this one will have to wait for another day when it's a bit less breezy! 😉

As the old saying goes: "It's better to be down here wishing you were up there than being up there and wishing you were down here!"

January 29

What surprised me was the tone of astonishment that a model aircraft can weigh up to 150 Kg. The other point seems to be that the only way to get civil air information to the military is to raise a NOTAM but the system doesn't allow existing UK AIP information to be put into a NOTAM. A case of heads I win, tails you lose.

Since there are going to be increasing numbers of drones flying below 400 ft and the military are allowed to low fly just about anywhere in the UK at not below 250 ft, it sounds like someone needs to find a way of getting civil air information to the military otherwise we will see an upsurge of AirProx reports and in the worst case a collision.

January 29

This morning made the 4th time I've managed to get in 1/2 day's flying in January! That being said, the cloud base was low and marred by even lower clumps of cloud. I had wanted to check on the KE mix, it's no more than 1 to 3 clicks, and to sort out the KE loop mix so that I don't have to lean on the elevator or aileron stick to get a perfectly planar half loop. However, the cloud was sufficiently low to stop that little game but I did work out a tweak to two so that might have done it. The next thing was to work on the roll combination. That is 3 x 1/4 roll in the same direction. So a definite line between each element and then 3 x 1/4 rolls in the opposite direction. Between rolls in different directions the change of direction must be immediate - FAI Aerobatic rules. However, after the first flight, when I disappeared into cloud clumps occasionally, the cloud all seemed to get much lower so I sat for an hour waiting for an improvement. Eventually, one came and I got in 3 more flights before I ran out of time. Only 2 of the roll combinations were dead level with no variation in direction of travel so more practice needed.

January 28

Will you be doing that at the field Outrunner or when you come home. I write my comments after I get the aircraft back to the pits as if I leave it till I get home I'll probably forget key parameters. But that just might be my old brain or rather memory bank!

January 28

On 27/01/2024 at 15:31, Erfolg said:

Does anyone have access to Naca 0018 cd/AOA plot looks like. I am particularly interested in the stall AoA (the approx., ignoring scale effect). Also the max lift drag AoA.

I have an idea what it might be, although I seem to make more mistakes these days. Plus the guy I used to discuss these things with, before I did anything, is no longer with me.

I'd use between 0.5 and 1 deg. 5 deg is far too much and would need a very tail high attitude to fly level. 2 deg is too much.

January 28

21 minutes ago, Geoff S said:

The router's working fine as it is. I have adequate data speed for both my wife and me to watch any video streams separately and simultaneously. The only s/w updates I want are those relating to security. I've written enough s/w in my time to be aware of the temptation to do just a bit more for personal amusement and satisfaction to be wary of it in commercial environments. I use an ancient version of MS Office Pro (97) which does more than all I need, and an equally ancient version of Photoshop likewise.

As hardware gets more powerful, much of the power is absorbed by programmers and data hungry high level s/w packages. I only use what I need or what I find useful.

Lot of truth in that Geoff. I still think Word Perfect 5.1 was the best word processing package I ever used. Lightning fast and the reveal/hid codes trick allowed you to sort formatting problems almost as quickly as the WYSISYG of Word, Only issue is, there is no way of knowing when it's a security patch or one of the more fanciful ones!

January 28

18 minutes ago, Martin Harris - Moderator said:

On a non-scale model, wouldn't the ideal solution be to route the battery/ESC cabling externally? No additional connections and absolute protection against inadvertent motor actuation until making the connection prior to flight.

That's what I used to use on my 2 m aerobatic aircraft. I just used a Jeti spark arrestor and a 4 mm plug on the positive lead that routed out through the fuselage. It was a requirement at the World Champs in Muncie in 2011 that the aircraft had to be disarmed when collected after landing. Never had a problem with a 4 mm plug and socket connector coming loose.

I don't do that anymore as it's just as easy to remove the canopy (slide back 2 canopy latches and lift off) and disconnect the Lipo to ESC connection. Of course, you could splash out on a Jeti electronic battery switch. There are 2 versions. One up to 100 A current and one up to 200 A current flow. That will allow you to arm and disarm the aircraft via a Tx switch. They do cost a lot of money though! Then again, they are designed to work with high current.

January 28

Geoff, my router supplier gold me not to turn the router off overnight as that'svwhen they upgrade the software router.

You may want to check your router's sofware standard with what your supplier tells you is the latest version just in case your router has not been updated.

January 27

3 hours ago, Rich Griff said:

A VTOL airfield would be so much smaller than a full size or even club airfield, meaning they could materialise almost anywhere, subject to conditions etc..

This could result in reduced or more regulated flying fields for us, compulsory rid and/or other conditions imposed by caa...

The CAA cannot get a VTOL airfield to materialise anywhere. The airfield will need planning permission and there will be lots of NIMBYs who stick their spanners in the works. Even for a helicopter landing into a field you do need to get permission from the owner and let the Police know. If you have a heli pad in your garden the same goes for planning permission.

Be good if you didn't just throw out misinformation like this RG.

January 26

3 hours ago, steve too said:

One of the best fly on the wall documentaries ever produced.

It wasn't a documentary. It was written by insiders to flag up the constant battle between the Civil Service and Ministers. Lesser ministers could be bamboozled whereas the really good ones ruled the roost. Trouble is, there aren't too many good ones!

January 26

I cannot see the relevance to model flying. We operate from a fixed location within a small chunk of airspace. We do not go cross country unless we are after some form of record flight in which case we will take appropriate action. Am I missing something?

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