Jump to content

Ever wanted to get into or improve your aerobatics?


Peter Jenkins
 Share

Recommended Posts

Hi Algy,

Re your question about checking CG in a 45 deg dive. I've not seen this method described before and I have not tried it myself. I think my initial reaction would be I'd rather be climbing than diving when doing trim checks like this. It's probably a tad more difficult to ensure that you have a constant speed in a 45 deg descent as opposed to a climb. You start the climb a lot lower than the dive obviously so it's easier to check for a constant speed on climb. If you have increasing speed, then you will start to get other aerodynamic forces that come into play e.g. wing/tail incidence may be out slightly and having trimmed for S&L flight it may not be right for a different speed. As you know, trimming always starts with the CG as any change in CG means you have to go through the rest of the trim checks again.

I think that's the only reason I'd stick with the 45 deg climb or even just fly S&L and then roll inverted and see how much down elevator (if any) is needed to maintain the flight path. You can be pretty certain in the latter case that you have achieved the two flight conditions at the same airspeed.

Peter

Link to comment
Share on other sites

I agree with you Peter, but I thought I would see what happened with my model as I am happy with the CofG and compare it with the 3D trim check method given, I expected the model to pull up but it didn't. I think the only advantage of the dive is that power / thrust line is taken out of the equation and that you can then rectify that later, it reminds me of the test that competition aerobatic slope gliders used.

Hi Stephen, don't panic just build up to it at height, no need to scrape the fin on the ground. If you are getting it upright every time you must be doing something right.

Link to comment
Share on other sites

Martin - I agree with you. I've heard that some pilots trim their aircraft nose heavy when upright so that you need the same amount of pull as you need push when inverted. There are other ways of compensating for the amount of push you need when an aircraft is inverted. You can increase the amount of down elevator and/or you can introduce exponential that increases throw when you push down. Alternatively, you just get used to having to push a long way to get level flight inverted. This may be an issue if you need to perform a negative flick roll (snap roll).

Stephen - you are not alone in feeling uncomfortable flying inverted. I also felt uncomfortable but after a couple of years of flying aerobatics I've pretty much cured myself - but not completely as I have yet to feel comfortable enough to do a low inverted pass! You, and the many others who share your concern, might find the following two suggestions useful:

  • set up a 45 deg climb and then roll inverted - at least you are climbing away from terra firma as you practice inverted flight
  • OR perform a large half loop and then fly inverted for as long as you feel comfortable before pulling the second half of the loop.

As ever, the only way to get comfortable with flying at odd angles is to keep practising but to make sure that you have a built in safety margin as described above. That reduces the adrenaline rush as you take on new manoeuvres.

Peter

Link to comment
Share on other sites

Well Peter, I tend to be with you about flying low inverted. I think it is to do with my days flying full size but I always fly at a hight, that should the fan stop at the front, I can at least get upright and turn into wind before arriving on the ground.

Flying inverted is down to practice, so if you set part of each flight to inverted practice, you soon get to a point when an inverted circuit and then figure 8 becomes comfortable (if not normal).

Just keep some safe height, I have payed for showing off low level (for a dare) and the very reliable motor picked the moment I was just a foot of the ground to stop and the one point (fin) inverted landing ended with a re-kitted airframe. It was a tatty aircraft so I didn't cry over it and would not be tempted with any of my current fleet.

Link to comment
Share on other sites

Some interesting comments on how people like their models to perform when inverted. Personally, I prefer not to have to input any elevator for straight and level inverted and trim my models accordingly.

I think the matter/skill of flying inverted is very much down to "state of mind" and also very dependent on the model being flown. For example, I can just about fly inverted circuits and eights relatively comfortably with a small 32" EPP foam model. However, transferring that to a larger, more expensive model is another thing entirely.

Talking of which, my new toy for 2014 will be a Sebart Angel 30e which is my Xmas pressie from my fantastic and wonderful GF.

Steve.

Link to comment
Share on other sites

Hi Steve,

Some true words. It is a state of mind with any form of aerobatics as to what you are comfortable with and to some degree the risk / price of a crash can hold you back. I am happy inverted with my 450 helicopter but get a little more twitchy with the 600.

I have an Angle 30e a great little plane that will do the book, the only down side I found is the duration in any wind. I used it at the NPOD and have flown it in winds of around 20mph without too much problem, just restrict the flight time to around 5mins in the wind. If you set it up with about half the movment on the elevator and ailerons it is smooth. Do use a good servo on the elevator and I would recomend extending the elevator horn and you will still need to come in on the servo arm, to get good elevator resolution and reduce the movement, once that is done it is very nice to fly. My one has now got over 22hrs flying on it, hope you enjoy yours as much.

Link to comment
Share on other sites

Thanks for the tips re the Angel Algy. I've always had my eye on one but for reasons I don't quite understand, I never got round to buying one. Then just recently, my ticker caused me to spend a week in the local hospital. So, I quit smoking 30 days ago and what was "fag" money is now model funds. So, with something of a second chance at life, my GF gifted me the Angel and I have the spare cash to kit her out. But, I digress.

By half movement on the elevator and ailerons I guess you mean half of what is recommended in the manual for "normal" flying and not those required for doing the crazy 3D stuff?

My aim is to set it up purely for pattern type flying as that's where my flying style has naturally developed.

Steve.

Link to comment
Share on other sites

Hi Steve

I'd be interested to learn how you set up your aircraft to be able to fly with no down elevator when inverted. Do you put up with a pull force when flying the right way up straight and level? I ask, because you will need to have the wing at a positive angle of attack to generate lift which ever way up you are and I believe that you can only achieve "hands off" for both conditions if the aircraft has very little stability. That will make it a bit twitchy. So, how do you manage that?

Re flying control movements, aim for an aerobatic rate of around 10-12 degrees movement on aileron and elevator and then adjust upwards or downwards from there. The only way to determine what control throw you need is to fly the aircraft and see how it feels.

If you continue not to smoke, you should end up with a tidy sum in your airframe budget! Once you have your Angel 30 trimmed out try out the Clubman Schedule which is here. Also, take a look at the video of the Clubman which is here. Don't be put off by it being called the Sportsman Schedule - the name was changed but not the schedule!

Peter

Link to comment
Share on other sites

my little mini-panic often ends up needing no elevator for inverted dependent on which battery pack is in it. A rearward C of G means it ends up with a shade of down trim for normal level flight and hands off inverted. It is a VERY neutral stability setup verging on unstable.  Low rates and bags of expo tame it.

I find it best to practice inverted with something disposable, but keep low inverted sessions fairly short - my EasyStreet met it's end when I spent a full battery practicing inverted figure 8s getting lower and lower - I dumb-thumbed the exit by pulling 'up' at about three feet altitudecrying 2

Another good model for practice is the Formosa 2, they were cheap as chips and tough as old boots.

Edited By Bob Cotsford on 19/12/2013 09:48:18

Link to comment
Share on other sites

Hi John, if you cannot move the battery then your only option is to add weight at the tail. If you have any CG measurements in the instructions, where is your CG in relation to those measurements? If there is no info on CG position, be very careful when you add weight. Start with 1 gm and see what it does to the amount of down elevator you need when inverted. Gradually increase the weight at the tail until you arrive at a position where the nose continues to drop but is easily held with a small amount of down elevator. You can also increase the down elevator movement (keep up elevator the same) or change the expo so you get more sensitive movement from down elevator immediately you start to push down tapering off as you go to full down elevator. Again, make small adjustments and one at a time so you can see what's going on from each adjustment.

Link to comment
Share on other sites

Hi Bob, at my stage of aerobatic learning I don't like flying inverted low especially as I don't have to do this until I decide to go for the C certificate. I'm working on that, but have yet to address the low level KE and roll from inverted to inverted! It depends on what flying style you want to develop, but I'm happiest when the model is stable and reacts predictably and smoothly to my inputs. That way, I can keep up with it or better still stay ahead of it!

I've had my share of flying low inverted and pulling when I meant to push and I have a long list of bin bag events as a result! These days, I prefer not to push my luck or skill and come home with the same number of components I packed into the car in the first place!

I take my hat off to you guys who can fly low figs of 8! I shan't be challenging you though!

Link to comment
Share on other sites

I have been following the above again and it still beats me as to why anyone would want to fly a model with zero elevator input inverted. Ever heard of a full size trimmed like this? It may explain why people inadvertently pull `up` and crash since the natural instinct if it was down trimmed would be to level it with a touch of up elevator when flying upright. Constant forward pressure on the stick is always a good reminder that you are upside down and shows a well set up model.` Hunting` for elevator neutral trim is another sure sign of a too rearward cg.

Link to comment
Share on other sites

Folks, we are extremely fortunate to have two great aerobatic pilots to provide their views - Martin and David H. It's not just the way I set things up so it's really worth giving considerable weight to what they say. As I said at the beginning of this thread, I've focused on setting up an aircraft for precision aerobatics rather than 3D - since I know next to nothing about 3D.

Another way of looking at this is that the further aft you move the CG the closer you come to an unstable aircraft. What that means is that if you are flying straight and level and a bit of turbulence nudges the aircraft into a nose up condition, the aircraft will continue to pitch nose up. Think about balancing a cone on its tip. You have to work hard to keep it in its balanced position. Let it get away from you and it will be very difficult to get it back to equilibrium.

Link to comment
Share on other sites

But trimming isn't all of the road to better flying..

Mentoring, critiquing are also very important to develop piloting skills. Or recording results on paper.

I've seen recording done at one of the international meets I went to. Either Belgium or Italy. The Japanese team manager had a multi-pen paper chart recorder mounted in a briefcase and was gathering "evidence" so they could learn about others' flying styles. They also did a lot of audio recording with various flyers.....(unbeknown to the pilots !)

Peter you mentioned the elevator + rudder stick path through "point" rolls. Like a diamond I believe you said. My thoughts on this was no, more egg-shaped but then it's hard to describe something that you do on "autopilot"!!

I hasten to add this is without any mixing, just a true, well sorted model. smiley

Link to comment
Share on other sites

My turn to second David.

I too witnessed the Japanese team pen recording every stick movement of the top pilots in Switzerland when I went as reserve/spectator. Very sneaky.

The left stick movement on mode 1 is indeed semi circular using a flowing motion rather than abrupt points. On eight points I have always flicked the aileron stick, allowing it to return to centre by itself which gives me a more even roll rate and lets me concentrate on the more important left to maintain level flight.

I could never have done very well without a mentor since I am not a natural flier as David is. Even though mine was an arch enemy at a comp. we would always do our best when calling for each other to give the flier the best possible chance of a good flight.

Link to comment
Share on other sites

Hi Steve,

Now these are the setting I have on my Angel 30e, that suit my flying I made new aileron horn 30mm from surface to connector and a elevator horn 25mm from surface to connector, out of 1.6mm G10.

High rate: Aileron 18mm (10% expo) Elevator 20mm (10% expo) Rudder 35mm (0%expo)

Low rate: Aileron 10mm (0% expo) Elevator 12mm (0% expo) Rudder still 35mm (30% expo)

CofG 3mm behind the wing joiner tube, it is smooth with the CofG in this position and spins well but will drop a tip if flown too slow. She needs just a breath on the elevator when inverted but I would suggest using a CofG in line with the back of the wing joiner tube.

Link to comment
Share on other sites

Thanks very much Algy.

Brilliant info which I'm sure will get me going in the right direction.

I'm a bit miffed with my LHS though as my Angel still hasn't arrived after what is now 17 days. The Spanish way of life does have it's pros and cons!? Now I'll have to wait until next Monday at the earliest to get my mits on the model.

Still, it will be a very nice slow assembly project over the Xmas holiday.

Steve.

Link to comment
Share on other sites

David and Martin - as ever, you are absolutely right in highlighting the role a good mentor can play in improving your flying. You both raise excellent points about analysing performance at the highest level and then using that information to assist your nation to improve its performance. I do not know how widespread this practice is but I am unaware of a similar tactic being used in the UK. If it is, then it would be interesting to hear what has been learned.

As we are dealing with people who want to get into aerobatics or to improve their existing aerobatics the value of a mentor is vital to both help and encourage people to take up and improve their aerobatic flying. I am unaware of any other initiative other than the GBR/CAA's New Pilot Open Days that provide at least one day's worth of mentoring. Perhaps this is something that it would be great to know about in this forum - that is what mentoring is available at your local club. If mentors are willing to help out both in their clubs and other local clubs they might wish to use this forum to flag up their willingness.

Equally, if you would like to have some help from a mentor then again an appeal on this forum may elicit some help. You can also PM me giving me the Club at which you fly and I'll try see if I can connect you with an experienced aerobatic pilot in your area.

Peter

Link to comment
Share on other sites

Peter IMAC do usually have a new pilots weekend at the beginning of the year when new and would be pilots are mentored for the weekend to date it's been held at Sudbury Derbyshire, I cannot confirm this for 2014 but I'm sure the program for the coming year will soon be posted on their website

 

PS they have in the past arranged BMFA "B" tests during the said training weekend for pilots struggling to get one in their own locale

Edited By Ultymate on 22/12/2013 08:19:42

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...