B J Craft Anthem build - 2 m FAI F3A class aircraft and Debowski TMCR contra

[Peter Jenkins]

Having established a position for the flight pack, the next job was to assemble the battery tray and glue it into position.  The tray I have chosen is easily removable since this makes any maintenance, or repair(!) of the undercarriage much easier.  The tray is all ply with 2 carbon tubes that fit into ply supports that are glued to the fuselage sides.  So, I dry assembled the battery tray.  The photo below shows the tray upside down so you can see the way the carbon tubes and central spar are attached.

 

 

The design for securing the carbon rods was a set of 4 supports that allow the rods to drop in vertically and then be secured by a shaped ply piece screwed together.  However, I wanted to reduce the number of screws to be used so turned the rear supports on their side.  This would allow the carbon tube to be slid into them and then the front drops into the front mounts to be secured with servo screws.

 

 

Once these supports were in place, I glued the carbon rods to the battery tray and place the tray and rods in position so that the glue would set with the rods in the optimized positions!  The photo also shows the front locking bracket and 2 servo screws that will secure the tray.

 

 

 

My original idea of mounting the Rx, battery back up and Flight Coach hardware on the mid point CG position raised the issue of how easily this equipment could be accessed.  However, by moving the mounting tray down towards the bottom of the fuselage looked like providing easier access than having it towards the top.

I made up a tray out of 1/8 in balsa with a 1 mm ply facing with some cut down TE stock to increase the gluing area and then stuck Velcro across it.

 

 

The idea was to mount the Flight Coach PCB, the Rx and the Optipower Ultra guard on it as shown.

 

 

Thankfully, as you can see, that was a viable solution.  The Flight Coach module, is connected to the large round black object that is the GPS compass and will provide the aircraft’s path relative to the points that will define the aerobatic box.  The Ultra Guard is powered by a 2S 450 mAh LiPo that sits under the PCB.  The balance lead is plugged into the socket at the bottom right of the PCB and I needed to be able to access this so that the LiPo could be unplugged and replugged to avoid current drain.

As a digression, the Ultra Guard senses the battery voltage being fed to the Rx and then sets a figure that is 0.5 v below that.  If it sees the voltage drop to that figure it will start feeding power to the Rx and will set the 3 LEDs flashing (you can just see them at the top of the picture).

 

I then drilled 2 x 3.5 mm holes either side of the Rx and Ultraguard and inserted a tywrap left loose.  Then it was time to epoxy the board into position.

 

 

 

[Peter Jenkins]

I also decided to the position for the 2S 850 mAh Rx LiPo.  I made up a balsa plate and glued that to the back of the wing tube and the frame that sits on the tube.  You can just see this in the photo.  Finally, I connected up the Rx to the Xbus lead and the 2 motor leads and fitted the 2 aileron fly leads.  These will be glued to the fuselage side so that I will just need to plug in the wing servo extension from outside the fuselage.  This arrangement avoids having to put a servo lock onto the aileron lead since the inboard end will be glued to the fuselage and the yaw thrust is very low.  This arrangement has worked without any problems on my previous 2 aircraft.

 

 

After connecting everything, I switched on the radio to make sure everything worked as required.  It did!

 

I then turned to fitting the 2 canopy locks to the canopy.  This requires some careful positioning of the canopy lock to avoid fouling the canopy structure and then cutting slots in the canopy to enable the locking lever to operate.  The final part is drilling a hole in the canopy arch on the fuselage for the locking pin to engage with.  I also glued 2 pieced of 2 mm ply to the rear of the canopy arch to support the engagement pin.

 

 

 

The final part of the build was to select a position for the Rx switch, make the ply plate to mount it onto and then glue it in place.

 

 

 

So, that concludes the assembly of the Anthem.  I will go over it with a fine tooth comb to double check everything before committing to the maiden.

 

 

I still have some setting up on the Tx to do but since that is a JR specific function I’ll just list what I will be setting up:

•  I use 3 rates covering: spinning, landing and aerobatics.  The control throws for aerobatics are less that 10 deg for ailerons and elevators and 35 deg for the rudder.  Landing gets slightly larger throws while spinning gives full elevator and rudder with ailerons at landing rates.
• I set up a number of logical switches – Stick position in JR parlance – that provide the following 

            o   A downline mix that is triggered when the throttle is fully closed.  This will give a slight amount of down elevator to keep any vertical dive from pitching towards the canopy in still wind conditions.

            o   Additional rudder deflection when full rudder is applied in Aerobatics mode – this is to provide additional rudder for stall turns

            o   Snap settings that will be triggered by pushing the right hand stick right into each of the four corners.  This triggers elevator, rudder and aileron deflections that I tweak to provide a clear pitch up, or down, from the elevator and a rapid rotation from rudder and aileron deflection.

 

More after the maiden on how the aircraft flies.

[GrumpyGnome]

Peter - how much life do you get from an 850 Rx LiPo?

Edited April 1, 2023 by GrumpyGnome

[Peter Jenkins]

I get 4 flights (8 mins to fly the FAI(P) schedule) and if there is >50% "life" remaining, I will fly a fifth.  Never (🤞) had the Ultraguard chip in - so far!  I always carry 2 Rx LiPos with me.  I aim to fly no more than 6 flights per session so I take 6 flight packs with me.  Usually, I'll just take 4 packs as I only get to fly a half day.

 

I found that my concentration started to drop off if I fly more than 6 flights per day each one being the full schedule.  Each schedule has 17 manoeuvres not counting take off and landing of course.  Flight time is usually 7 1/2 mins but I allow for 8 mins.

[GrumpyGnome]

Cheers Peter.  I can only imagine the concentration required!

[Peter Jenkins]

Was out getting in some practice with my current F3A bird today!  Cold and windy but good to blow the cobwebs off.  Now just waiting for slightly calmer conditions for the maiden.

 

[Philip Lewis 3]

On 01/04/2023 at 14:39, Peter Jenkins said:

I get 4 flights (8 mins to fly the FAI(P) schedule) and if there is >50% "life" remaining, I will fly a fifth.  Never (🤞) had the Ultraguard chip in - so far!  I always carry 2 Rx LiPos with me.  I aim to fly no more than 6 flights per session so I take 6 flight packs with me.  Usually, I'll just take 4 packs as I only get to fly a half day.

 

I found that my concentration started to drop off if I fly more than 6 flights per day each one being the full schedule.  Each schedule has 17 manoeuvres not counting take off and landing of course.  Flight time is usually 7 1/2 mins but I allow for 8 mins.

My results concur with yours Peter, as it happens I use two 500 mah isolated LiPo's so slightly more capacity than your 850 mah, I get 6 flights and that's the max I do in any one sesion (no back up but I have telemetry warnings set up instead), packs are pretty much at storage charge after six eight minute flights.

[Peter Jenkins]

I calculated that each P schedule flight took 80 mAh.

[Peter Jenkins]

Having set up the Tx, my biggest problem was trying to get the twin motor setup to connect to the 2 throttle curves and the 2 associated mixes.  This is because the D3 ESC requires four idle settings as follows:

 

·        Ground – closed throttle shuts down the motors

·        Spin – set for around 300 rpm

·        Land – set for about 100-200 rpm

·        Aerobatics – set for 1,300 – 1,500 rpm

 

The recommended rpm for 50% throttle is around 3,000 rpm and full power with wide open throttle.  I only ever felt I needed more than 80% power once and that was to when checking out the up/down thrust.  So, there is plenty of power from this combination.  Incidentally, Debowski recommends 23 x 20 props for front and rear although he says that the 22 x 20 props are OK for “light” airframes like the Anthem.

Incidentally, the all up weight of the aircraft with and without the drive batteries is as follows:

 

·        Weight without drive battery pack = 3,805 g

·        Weight with drive battery pack       = 5,008 g

 

The FAI requirement is that the weight of an electrically powered aircraft shall not exceed 5,000 g but they allow a 1% variation so up to 5,050 g would be acceptable.  In any event, I have flight packs that are lighter and would drop below the 5,000 g limit.  For domestic competitions, this is not an issue.

In the end, fiddling around with the 2 ESCs proved too taxing so I went back to a single motor channel and connected the 2 ESCs via a Y lead!  That took me 15 mins to set up!

 

So, the great day arrived and I ended up at the patch in the afternoon to be met by a cloudless blue sky – I hate those conditions as it’s so easy to lose the aircraft against the blue sky – and a lowish wind speed but at 90 deg to the runway! 

 

After assembling the model and checking everything over yet again, I did the obligatory range check and got a club mate to move the model through 4 quadrants to check the radio reception while doing the range check.  All checked out as did the Failsafe check.

 

 

 

 

This photo shows the wing sweepback very clearly.

 

So, carried the Anthem out to the runway, walked back to the Pilots’ Box and opened up the throttle to half power.  The wind chose that moment to send in a strongish gust of wind that required use of the rudder to maintain the take off track!  Once airborne, the aircraft felt distinctly odd and had a marked yaw to the left.  It took quite a few beeps of rudder trim to sort that out.  Interestingly, when back on the ground I looked at the fin/rudder alignment and it was perfect!  I can only conclude that setting up the rudder in my shed where I don’t have the space to take a step back was not a good idea!

 

I was expecting that there would need to be some elevator trim and some aileron trim required to enable hands off level flight.  I was not wrong.  After landing, I could see that the elevator required 20 clicks of up elevator and the ailerons about 8 clicks of left aileron.  There is no adjustability for the tail plane so I will need to tape the elevators in their current level flight position and adjust the pushrods to allow the servos to go back to neutral.

The aileron trim can be taken out by adjusting the wing incidence.  Since the port wing was producing a tad too much lift and causing a bank to the right, I needed to reduce the port wing’s incidence.  This requires the incidence adjuster to be turned clockwise to move the wing down.  Before doing that I loosened off the rear adjuster clamp and the wing bolt and turned the adjuster a quarter turn then secured the clamps. 

 

On the first flight, I also carried out the standard CG position check by pulling up to 45 degrees and rolling inverted and then releasing the elevator stick.  The aircraft pitched slowly towards the canopy which was what the designer suggested was ideal.  I was using the mid point of the CG range that the designer had used.

 

The landing produced a hear stopping moment when at about 2 ft off the ground, and having almost completed the round out, I closed the throttle as I would normally do – quickly!  Wrong!  The D3 ESC is the fastest acting ESC there is and as it directly controls the prop speed even when slowing down it was as if an air brake had been applied.  The aircraft dropped onto its u/c and bounced a little!  To solve this problem, I raised the landing idle speed and also determined not to take power off too quickly during the flare!

 

The second flight was much better as regards its general smoothness although I had omitted to reduce the aileron rate from 30% of full rates.  After landing I reduced that to 25% and will check that at the next flying session.

 

I tried upright and inverted spinning on the 2^nd flight.  The upright spin is clearly a spin but quite slow whereas the inverted spin was a bit of a waffly affair.  I will have to see if I can get any move down elevator to help to keep the wing stalled or, if that doesn’t work, then I’ll use a mix on the rudder to bring in a small amount of in-spin aileron.  A point to remember for inverted spinning is that the aileron needs to move in the opposite direction to the rudder.,

 

The vertical up line was now straight as a die and so was the downline as regards the yaw axis.  I had used a mix from fully closed throttle to five 5 units of down elevator to keep the downline vertical in zero wind conditions.  Two trial downlines showed a slight tendency to pitch to the canopy so after landing I increased the mix to 7 units of down elevator. 

 

The next check was for Knife Edge.  What I was looking for here once I had established a roll to wings vertical was whether there was a pitch to/from the canopy and whether the roll increased or decreased.  The JR XG11 helpfully has a pre-set mix for rudder as master and elevator and aileron as slave.  Turns out that the aircraft pitches to the canopy and the roll tends to decrease on both knife edges.  Solutions are to try moving the CG aft to see if that reduces or eliminates the problem or use the KE mixes.  That’s for the next flying session.

 

I checked both the side thrust setting (0 in this case) by pulling to the vertical and applying power and checking to see that the aircraft went straight up without needing any rudder correction.  This is close but not quite there.  I was using 4 clicks of trim for each beep of the trimmer for the initial flights but I have now set this to 1 click per beep for more exact trimming.

 

The other thing was to check the down thrust was correct.  I flew in straight and level at my datum throttle setting of half throttle.  The JR XG11 has a stick alert that I set to beep at 50% so that I know I am at half throttle.  As the aircraft passes in front of me I smoothly open the throttle to full power.  I am looking to see if the nose rises or falls immediately.  If there is no change in this instantaneous attitude then the thrust line is correct.  The aircraft will start to climb of course once the speed rises but I’m looking for that instantaneous change.  That worked out fine so I was happy that will not need any tweaking.

 

As a side issue, I keep some mixes on a switch that is separate to the main Flight Mode switch.  The downline mix is one of these and the other is the knife edge mix.  I switch these out as part of my landing checks to make sure that I have the aircraft correctly configured for landing.  Landing with the downline mix active is exciting as the nose pitches down as you close the throttle when you are less than a foot off the ground!  With my other F3A aircraft, I don’t have an idle set for aerobatic flying as the prop braking function only works when the throttle is fully closed.  With the D3 ESC with its governed rpm this is no longer the case as braking is there at any throttle opening.  So, for those aircraft, I select an idle of around 100 rpm.  That gives me an instant response to throttle even from fully closed which is very useful when you just want to add a touch of power to counter a slight under shoot as you don’t have to move the throttle several clicks up from idle before the motor suddenly bursts into life and gives you a bit more power than you intended!

 

There are a lot more trimming flights required to get the aircraft fully trimmed out – probably a total of 20 – covering all sorts of things such as: spinning, speed of snap rolls, lateral balance checks, general feel of the controls to get roll and pitch rates right.

 

The other interesting thing was the difference between the fuselages of the Element (my current F3A aircraft) and the Anthem.  As you can see from the photo below, the Element has a taller fuselage, around a couple of inches, compared with the Anthem.  The two fuselages are exactly the same length so you can see that the Element appears to be a little dumpy in comparison.

 

 

I will post again once I have finished trimming and have flown the aircraft through a number of times with the current FAI schedule with my views on the Anthem and Debowski TMCR combination.  Right now, I would say that even after just 2 flights it’s very promising.

 

Having returned home, I set about preparing the aircraft for its next trimming session by adjusting the rudder and elevator linkages so that the control surfaces were in the trimmed position but with the servo back to centre.  So, the rudder now looks like this with the servo at neutral.

 

 

I’ve also increased the idle speed for Land and will try and remember not to close the throttle till the aircraft has landed!

[Peter Jenkins]

I have now flown the Anthem in two more sessions.  

 

I am increasingly impressed with the motor system - the TMCR and the 2 D3 ESCs.  With the recommended 23x20 props, the motor has excellent power, far more than would be needed normally but as Adam Debowski, the designer, says, it's helpful to have the extra power on high wind days when you have to drive the aircraft forward against the wind to get the geometry of loops right.  

 

I should also correct anyone who thinks that I said the ESC provides air speed control.  It provides prop speed control.  That means you still need to use the throttle for uplines, 45 deg climbs and downlines but you only need to move the throttle about 3 clicks for a 45 up line and 4/5 clicks for a vertical upline.  You still need to use the throttle though!

 

Talking of up and down lines, the geometry of introducing more downthrust into the motor mount is bringing the bottom of the rear spinner a little too close to the nose ring.  So, I've experimented with a mix from THRO to ELE that comes in from a few clicks after the datum S&L setting to give a touch of down elevator.  Today, I spent some time refining this and I think it is now just about rock solid on the upline hands off.  Of course, that doesn't mean to say that it's that simple as you need to lean the aircraft into the head/side wind to compensate for the wind direction affecting the aircraft's position over the ground.  The downline is again achieved as hands off with a mix triggered by a fully closed throttle and as per the upline needs management in strong winds to achieve a vertical downline with respect to the ground.

 

The spin is now almost sorted as I ended up with a significant in-spin aileron mix triggered by full down elevator and full left or right rudder.  I manage the upright spin by manually using the ailerons having turned down the aileron movement in SPIN mode.

 

The snap roll on the 45 deg up line now seems to be sorted as the snap rate is now sufficiently slow that I can usually catch the aircraft after the 1 1/2 snaps with wings almost level and by recovering the elevator to a touch of up, the aircraft attitude is close the the entry 45 deg.  Guess I'm always going to lose points on this one until I can figure out how to stop the snap at exactly 1 1/2 snaps and on the 45 deg line exactly!

 

Landing continues to require a high degree of concentration as even closing the throttle a small amount makes a significant difference to the aircraft's speed.  I am getting used to it slowly though.

 

Overall, the aircraft is showing a significant improvement in its handling compared with the Element.  BJ has clearly made a number of small changes in geometry and aerodynamics that gives the swept wing Anthem an edge over the Element.  At least that justifies my decision to buy the Anthem rather than soldiering on with the Element.  That having been said, the D3 ESC gives the Anthem by far the biggest improvement over the Element that has to use the Jeti Spin 99 ESC as the contra in the Element, the Ralph Schweizer CRS, cannot use the D3 because of its rapid response to throttle movement.

 

I'll post again once I have finished this initial trimming phase and after I have managed to get the Flight Coach hardware installed and have worked out how to set it up and use it!

[DaveB1]

Fascinating, thanks for sharing with us mere mortals Peter

[Peter Jenkins]

I felt that I needed a bit more elevator to make sure that the wing stayed stalled when the spin was entered.  The longer servo arms arrived today and so I swapped out the smaller arms.  As you can see from the photo, I'm only using a slightly greater arm length.  The elevators now are able to just close the V gap between the tail plane and the elevator without stalling the servo.  So, the next time I'm out with the Anthem I'll see how the spin goes with the slightly greater elevator movement.

 

[Peter Jenkins]

Just put in another 5 flights on the Anthem taking total flights to 21.  Had the field to myself apart from when the Chairman turned up to have one flight with his heli.

 

So, the CG position that I have pushed the flight packs back to (4 cm aft of the battery tray front) seems to be fine.  There is around 2 clicks for elevator and aileron in the KE mix so my next move will be to make and glue in some new battery tray retention brackets thus allowing the packs to sit on the whole tray and not just half the tray!  That will also allow an even more rearward CG (I started at 300 mm aft of the wing LE at the root with the aft limit quoted at 330 mm).  Not sure exactly where the CG is with the pack in its current position - will have to do a rough balance at some point.  If moving the CG back even more towards 330 mm eliminates the need for the KE mix without affecting other aspects of the aircraft's handling I might be tempted to do that.  However, that may cause an access problem to the Rx battery and the Ultraguard as the latter needs to be switched off the Rx battery is switched off.  Something to watch!

 

The new longer elevator servo arms have allowed me to reduce servo movement from 135% back to 100% and this in turn reduced the misalignment at full down elevator to just a smidge.  Interestingly, full up elevator has both elevators in exactly the same position.  However, the increased elevator movement, which to be fair, was not really very much as the V in the TP/Elevator is closed, doesn't seem to have affected the spin as much as adding in-spin aileron.  I have gone back to a mix for the inverted spin using the rudder as master and the ailerons as slave to give a repeatable aileron deflection.  The aircraft seems to favour spinning to the left when inverted so I'll stick with that but going right might need a bit more aileron.  That's for next time's trimming session.

 

The snap speed is now fine provided I don't overdo the throttle!  Interestingly, I tried both inverted and upright snaps and both seem fine.  It's all now down to timing and catching the attitude as the snap is exited.

 

I tried the rudder at very low speed and at the very high speed and that showed that left rudder always produces a left yaw in both cases.  A full size test pilot with experience of swept wing jets suggested I try this as on the Hawk the yaw from the rudder reversed between low and high speed.  This is more to do with the Hawk's rudder being above the fuselage centre line unlike an F3A design where the rudder area is equalised above and below the fuselage centre line.

 

I had a couple of flights to try the current FAI P schedule and was surprised at how well the aircraft tracked and at the tremendous speed control the TMCR/Dc combo provides.  I think this is going to be an excellent aircraft provided I don't screw it up with piloting errors - all to easy!

Edited April 22, 2023 by Peter Jenkins

[Peter Jenkins]

Having started with the CG at mid point (300 mm aft of the root LE), I had moved the main pack back a further 70 mm and nothing seemed to get worse but the amount of mixing required for knife edge reduced.  So, as I couldn't move the pack any further back without falling off the battery tray, I've moved the tray back by 70 mm.  That will allow the pack to sit squarely on the tray and I'll be able to experiment with moving the CG a bit further aft to see if things improve or get worse!

 

The only issue was that access to the wing bolt location that was in front of the wing tube is now blocked - see at the bottom left just below the rear tray support!  So, have now had to use the alternative wing bolt position behind the wing tube.

 

[Giuseppe]

Hello Peter
I'm considering replacing my LEVIOSA and doing a market research I saw that both the ELEMENT and the ANTHEM meet my goals, so I read all your beautiful and very useful ANTEM build log.
I seem to have understood that the ANTHEM for the type of wing is more performing than the ELEMENT but it must be flown more carefully while the ELEMENT is quieter it is because I am not a pilot like you used to being in the first races positions but I usually occupy positions at the bottom of the rankings.....to conclude, do you think the ELEMENT is better for me?
Thank you
Greetings
Joseph

[Martin Harris - Moderator]

Welcome to the forum Guiseppe and thanks for re-posting in English as per the forum rules.  

You are welcome to use your own name though and don’t need to translate it to Joseph (unless you particularly want to!)

[Peter Jenkins]

1 hour ago, Giuseppe said:

Hello Peter
I'm considering replacing my LEVIOSA and doing a market research I saw that both the ELEMENT and the ANTHEM meet my goals, so I read all your beautiful and very useful ANTEM build log.
I seem to have understood that the ANTHEM for the type of wing is more performing than the ELEMENT but it must be flown more carefully while the ELEMENT is quieter it is because I am not a pilot like you used to being in the first races positions but I usually occupy positions at the bottom of the rankings.....to conclude, do you think the ELEMENT is better for me?
Thank you
Greetings
Joseph

Hi Giuseppe

 

Firstly, I have never been in the first 3 places in any of our FAI(P) competitions - unfortunately!  So, I am more like you than you think!

 

I have only flown the ELEMENT and ANTHEM  with a contra prop system.  The contra systems are different and so are the ESCs.  My ELEMENT has a RS CRS contra with a Jeti Spin 99 ESC.  The ANTHEM has a Debowski TMCR contra with the Debowski D3 ESC.  In my opinion, the D3 ESC makes a very big difference from the Jeti Spin 99.  This is because the D3 will hold any prop rpm that you select with the throttle stick.  For example, if you have half throttle and that gives 3,000 rpm. then when you dive the prop rpm stays at 3,000 and the D3 ESC provides braking to keep it at 3,000 rpm.  The Jeti Spin 99 only provides braking when the throttle is fully closed and you can adjust the amount of braking using a Jeti box.  The same, if you climb without touching the throttle, the D3 ESC will supply power to the motor(s) to maintain 3,000 rpm.  You will need to add power to keep the speed constant in a climbing manoeuvre but you will not need to move the throttle as much as with the Jeti.  So, it is, in my opinion, much easier to maintain a constant flight speed with the D3 than the Jeti Spin 99.  Unlike the Jeti, there is nothing to change in the D3 as it is all set by the manufacturer and seems to work very well.

 

As regards the difference between the ELEMENT and ANTHEM airframes, I would say that the ANTHEM is slightly better than the ELEMENT.  in the same way, I found that the ELEMENT was slightly better than the AGENDA, which was the design before the ELEMENT.  They both fly in a very similar way but if you are looking for the better of the 2 I would recommend you buy the ANTHEM.  

 

If you want to fly either with a single prop then I would recommend that you use the D3 ESC as that will give you much better speed control than a Jeti Spin 99 for the reason I gave above.  BJ Craft state that there is no side thrust needed for a single prop on the ANTHEM  whereas for the ELEMENT, you need the fuselage with a nose ring set for side thrust.  I have not flown the ANTHEM with a single prop but with a contra it's ability to hold a vertical line without yawing is very impressive - this is down to the swept wing of the ANTHEM.

 

So, you need not worry that the ANTHEM will be less easy to fly than the ELEMENT.  Obviously, you need to setup and trim both to get them to fly in the way that suits you but once you have done that then you will be very happy with either.

 

I hope that has answered your question.

[MattyB]

On 06/04/2023 at 01:31, Peter Jenkins said:

As a side issue, I keep some mixes on a switch that is separate to the main Flight Mode switch.  The downline mix is one of these and the other is the knife edge mix.  I switch these out as part of my landing checks to make sure that I have the aircraft correctly configured for landing.  Landing with the downline mix active is exciting as the nose pitches down as you close the throttle when you are less than a foot off the ground!

I understand why you keep them on a separate switch to the flight mode, but could you not just have them auto disable at the point you select the Landing flight mode? Does the XG11 not have the ability to use a Boolean logical switch i.e. Mix switch in position X AND flight mode does not equal Landing?

[Peter Jenkins]

Hi Matty,

 

Yes the XG11 does have logical switching and I make use of that capability.  Remember that the XG11 was launched in 2011 and the firmware upgrades stopped when the original JR company went bust as a result of financial wrong-doing in 2013/14.  The biggest problem is the limit of 6 mix programmes.  Currently, all 6 are in use so mechanical switching is now the only option.  The downline mix is needed for both Spin and Aero mode so just as easy to use a switch.  I am also using the same switch for the upline mix and there are times when I want that mix out.  I always do 'downwind" checks as I used to in full size which will come into their own when I get my P51 operational as that will then include a mode for landing covering u/c, flaps and trim.

[Peter Jenkins]

You may have noticed that there has been a gap between the last flight report on my Anthem.  There is a very good reason for this.

 

On the 22^nd flight, I had planned to fly another trimming session and to re-check some earlier trim settings.  My first check after take off and a 180 deg turn was to check that the thrust line was still providing no pitch change at least for the immediate period after the throttle change.  I used around 85% power for this check and as all was well, reduced power back to datum and then commenced my turnaround manoeuvre which was a half reverse Cuban 8.  Unfortunately, soon after establishing the 45 deg climb, I heard a loud crack and felt that I had lost all control.  The aircraft had by now rolled to the right and with a shock, I saw there was no starboard tail plane.  I had reduced power once I heard the cracking noise and the aircraft gradually pitched nose down.

 

At this point, I felt that my control was so degraded that the aircraft might end up in a total loss!  However, by using almost full left stick and some up elevator as well as advancing power to datum, I found I could level the aircraft.  It was on the downwind side of the airfield so I set up a gentle descent with a view to landing off a long approach.  The aircraft was heading towards the crop and on urging from my colleague I decided to try a turn to the right and then turn back onto heading so I could land on the full-size runway.  The roll to the right was easy enough but rolling back and then rolling left proved to be much more difficult.  By the time I had the aircraft back to wings level, it was heading off the runway onto some rough grass.  However, the ground speed was low as there was a strongish wind blowing and I was headed directly into it.  I managed, or at least thought I’d managed, to flare the aircraft for landing, some 50 yds away from me, which appeared to be quite a soft landing.

 

On reaching the aircraft, I saw that the starboardd tail plane was still attached but when I got the aircraft back to the pits and looked underneath, there was no bottom sheeting there.  The elevator and the servo and push rod were also missing.  See photos below.

 

   

 

After communication with B J Park, the Anthem designer, he put the finger on the JR 3301 servos I’d used for the elevators.  In his view, the plastic gears were on the weak side and putting a long servo arm onto this servo was the most likely cause of the gears stripping.  Now, I’ve used plastic geared JR and Futaba mini servos for elevators for a long time and I had never heard that the 3301 was considered to have a weak gear train.  However, there was no disputing the fact that both elevator servos had stripped their gears.

 

Assuming that the starboard elevator servo gear train failed just after I pulled up into the 45 deg climb, this would have allowed the elevator to flap away and lead to flutter inducing force on the starboard tail plane.  Flutter is usually denoted by a buzzing noise and I never heard this but then again, the aircraft was about 200 m away from me.  Flutter is exceptionally destructive over a very short period of time.  This would have accounted for the structural destruction of the starboard tail plane which had the bottom section ripped off and the elevator, with servo still attached, went with it.  I had put a servo lock on the elevator lead and that was still attached to the socket in the fuselage!  Perhaps it was a good thing the elevator lead managed to break free avoiding having the servo and elevator flapping around interfering with the rudder.

[Peter Jenkins]

I felt it prudent to replace both tail planes since I had no idea what the port tail plane had been subjected to.  The other piece of damage was to the starboard u/c leg that got stuck in a hole in the rough grass and damaged the section bolted to the u/c plate.  The fuselage also showed signs of a crack running aft from the join between the u/c box and the fuselage side.  A short while later when re-checking the aileron throws, I found that both aileron servos, Futaba BLS153s, developed a jitter when I placed the control surface throw measuring device on the aileron.  The BLS 153 has plastic gears yet has never given me any problems in other installations.  Since the jitter disappeared as soon as I moved the aileron stick I decided that the shock of the flutter failure may have damaged the 153 gear trains and since the ailerons were at neutral at the time of the flutter incident the damage would have been to those gears in contact at that position.  Thankfully, they were no so damaged as to cause a problem with control but I was not prepared to use them unless I could replace the gear train.  Guess what – no supply of gears!  So, 2 new aileron servos were needed as well.

 

In the end, I’ve ended up with all MKS servos as follows:  Ailerons – HV 737; Elevators HV 69, Rudder HV 747 (originally fitted).  I also replaced the aileron and rudder control rods with Secraft 3 mm turnbuckles and 3 mm ball links.  I had carefully examined the elevator pushrods and they were sound so I re-used them.

 

So, why had I used long control arms on the original elevator servos?  Well, I had used the provided elevator horns without checking how far the clevis hole was (there was only 1) from the elevator surface.  Turned out that this distance was 30 mm.  The standard JR arm only went to under 20 mm hence the need for the longer arm in order to get full elevator movement – by full I mean that the elevator contacted the tail plane.  The seeds of the over stress of the 3301 gear train were, therefore, the direct result of an overly long elevator horn.  Unfortunately, the geometry of the elevator horn did not allow space for drilling another hole closer to the elevator surface.  Rummaging around in my bits container, I came across some ZN Line metal horns with a distance of 20 mm from the base to the clevis hole.  They were retained by quite small 2 mm wood screws.  I sent off for a selection of 2 mm wood screws of increasing length.  Turned out that the elevator was thick enough to allow a 15 mm length screw to be used without reaching the other side of the surface.  So, that’s what I used.  Having cut the thread, I put a drop of thin cyano into the screw holes to toughen up the balsa.  I tried this out on the old elevator where the control horn join to the elevator had failed.  It was epoxied in place!  With the ZN Line horn in place with the 2 x 15 mm long screws, I could not exert enough force using my thumb on the horn to break if out of the elevator.  I thought the 15 mm long screws would do the job.

 

B J Craft build 2 new tail planes and sent them over by air mail in just over 2 weeks.  So 3 weeks after the near fatal incident, I was at the field again with the Anthem ready to go.  I had a degree of trepidation as I opened up the throttle but the flight went off uneventfully.  As it happened, despite changing all the control rods and 4 of the 5 servos, I only needed 2 clicks of up elevator, 2 clicks of right rudder and 4 clicks of right aileron to get the aircraft flying S&L. 

 

You may recall that I had started with the CG at the mid-point of the recommended range – 300 mm aft of the wing root LE.  I then moved the battery tray back by 70 mm to move the CG further aft – about 305/6 mm aft.  On my second flight, I decided to try moving the pack back a further 70 mm and this gave a neutral handling aircraft – probably gave a CG of 310 mm which is the aft limit.  I always feel uncomfortable with this situation!  The spin still required about 20% of in-spin aileron so there was little to be gained from the aft CG.

 

So, for the 3rd flight, which was the P23 schedule, I reverted to the CG of 305/306 mm aft.  The aircraft performed better than the pilot managed!  None of the tweaks I had introduced during earlier trimming needed revisiting so now I can focus on practicing for my first competition. 

 

Needless to say, it was a huge relief not to have lost the whole aircraft which, at one stage, seemed inevitable!

[Colin Carpenter]

Peter ! You a very lucky chap and obviously a very good pilot. Congratulations! As Corp Jones would have said - you didn’t panic !😂😂

[Peter Jenkins]

Ah Colin, there was panic!  And then there was too much to do and think about so panic got pushed to the back of my mind!  There was a lot of adrenaline though and that took some time to dissipate!

[Colin Carpenter]

I remember reading about John Cunningham,DH test pilot , sorting out a night fighter Mossie blown all over the sky by exploding He111 of Ju88. His navigator was in awe of his calmness. Reminds me of that. Well done. 

[Peter Jenkins]

Thanks for the kind words Colin but what I did bears no comparison with Cats Eyes Cunningham's achievement when 2 lives were at stake at night.