Strip Flying Skills Diploma, The most fun I have had with my clothes on!

Strip view

As an FI(R) at Cambridgeshire Microlights school at Chatteris, I was looking for an additional challenge that would help me on my journey towards becoming an FI, the strip flying diploma seemed to fit the bill. It covers performance planning, which will become key when we move to 600Kg Microlights, theory, planning and practical flying, thus it ticked all my boxes. I spoke to the instructor who trained me originally Mike McLoughlin as he is listed as being able to teach the strip flying course, as is the CFI Katie Denham, Mike agreed to teach me and we put a date in the diary.

Before the first day of training, I was sent links to SafetySense leaflet 12, Strip flying and 7c, Aeroplane Performance to review. On the first day of training for the strip flying diploma, we reviewed these documents and then calculated the performance of the aircraft we were going to fly, an Ikarus C42A, we also covered the theory of short-field takeoff and landings before getting into the aircraft to see what we could achieve.

On the first flight, I flew an uninstructed short-field with Mike, this was to set the benchmark, it wasn’t too bad I thought, Mike gave me some pointers and tried again and I took some more distance off and so we kept refining it, I think by the end of the lesson I had taken around 50 or 60 meters off the landing. This, however, this was on a long runway, so was just an exercise on short-field takeoff and landing.

We planned to follow up in a few weeks to consolidate what I had learned and fly into a short strip or two, however a combination of bad weather, teaching commitments and then the Covid Lockdown meant it was many months before I could finish the diploma.

Taking strip flying to the next level

Finally, the opportunity came on a windy and gusty day in September, this gave the opportunity to test my skills in a crosswind too. We first flew a couple of circuits at my home field using what I had previously learnt, the runway there is 430m so plenty of room if it went wrong. Next, we flew to Wingland, a much shorter strip at 250m. The approach was quite turbulent but with no real obstructions, I managed to land the C42 in about 70m on the first attempt and then taxied in where we were met by two club members. They were very welcoming, making us coffee and offering biscuits too, they commented on how short the landing was and that many visitors use most of the runway, guess the training was paying off! After coffee we flew a few circuits with Mike pointing out improvements and tweaks.  A few more circuits at Wingland and I was getting down to a full stop in a little over 50m. Time for lunch,  so we flew to Fenland where you can always get good food and Ray on the radio does a great job too.

Wingland Strip Flying

Well Wingland was good, but a greater challenge laid ahead! Mike took me to a private farm strip and demonstrated the approach and the dangers of the field, little things like 132kV national grid pylons on the approach, 11kV wires on the go around, and final was through a gap in some trees, oh and the strip was a little shorter for good measure too. The amount of turbulence on the approach as we passed through the trees was concerning, but Mike’s mentoring and demonstration gave me confidence and it was soon my turn. We discussed the abort point if needed, however the short field takeoff saw us high above the 11kV wires long before we got to them. 

Cross and downwind on the 500ft circuit were not an issue and then we turned parallel to the 33kV lines on the base leg, ensuring we didn’t get blown into them! I set up the approach and prepared to fly through the turbulence; again we were bounced around, but keeping calm and following Mike’s instruction we flew through it and I landed in about 50m. We sat and discussed the circuit flown and we went again, and again and again… each time adding more and more precision. I can’t tell you how much I enjoyed the challenge and with Mike’s instruction, and at no point did I feel unsafe.

Strip view Farm strip

I really cannot recommend this training course enough, no matter if you are recently qualified or have flown for a long time, this is a great course to push you to the next level.

A good camera angle even makes a 220m strip look long from the ground, but not so from the air!

Post lockdown engine blues, Rotax SMD ignition modules

mags before

Our Rotax 912UL has never started as well as it does now, but that wasn’t always the case!

 

 

Our aircraft had the post lockdown blues and so did we! The first time starting her and she would turn over, but not firing, there was simply nothing there. Others offered the normal advice, you know the normal things people say; make sure the throttle is fully closed, pull the choke fully out and run the electric pump for a couple of minutes! well yes, I had done all of that, next comes the offers to start her for me, they tried and failed too.  I remembered an article which said to warm the ignition modules with a hot air gun if you are having trouble starting. Hot air gun in hand I warm the modules for a few minutes, hastily getting back in and pressing the start button and the engine sprang into life! I warmed the engine before shutting down and putting the cowling on. Others experienced similar issues starting her over the next few flights when the engine was cold.

Then the battery gave out,  low voltage of a failing battery could cause the issue so this was probably the cause. After replacing the battery we could not start her due to the weather and the next day Gary Masters was due to do a service. Service done, it was time to do a ground run, I hit the start button and she turned over but didn’t fire! Gary came over and poured very hot water over the mags and she starts and runs perfectly. Gary then confirmed our suspicions that the Mags aka ignition modules have both failed! 

 

mags before

 

These Ducati modules have a reputation for failing and being expensive to replace, circa £1,500 a pair. In a BMAA magazine I had read of some recently approved modules from a company called Light Flight who are selling IGNITECH modules, I text the number on their website and shortly after had a phone call from a very helpful Andy Buchan. Andy told me the modules were approved for use by the BMAA and have been in use across Europe for some time. We purchased two modules with long leads and a simple bracket for £320.00 inc P&P, quite a saving, especially as they claim to be longer-lasting due to being mounted within the cockpit away from heat and vibration. The Modules have an option to boost the spark via a 12V feed taken from the starter solenoid switched positive. The boost ensures a full-strength spark at the low starting rpm. There is also a soft-start software option which we have not enabled currently as it doesn’t seem to be necessary.

Now with the new battery and the new spark boosting mags our Rotax starts effortlessly on the button. We could view it as we had to spend £320 or the way we see things is we saved £1,180!

The fitting is not difficult, but not straight forward either, as they are fitted inside the cockpit on the back of the firewall. This means drilling a hole of approximately 25mm to enable the pre-made cables to pass through, we then closed the hole by placing a piece of split pipe over the cable, thus protecting them and filling the hole. The wiring for the boost is simple, consisting of connecting 1 wire from each module to the switched solenoid terminal (Warning, ensure the battery is disconnected before connecting). 

We added a backing plate to the bracket to ensure airflow around the modules, they run warm to the touch the manufacturer says up to 50 degrees C. The 2 white blocks are voltage regulators for the supplemental supply and come with the modules pre-wired.

Would I recommend these modules? It’s early days, but with the ease of starting we now have and the fact they have a proven history in Europe, I think it’s worth the extra effort to fit these, not only because of the saving, but they have a spark boost and hopefully a longer life too!

Stratux EU or Pilotaware?

Back on 08th Aug, 2015 Stratux made its debut and it wasn’t many releases later that I built one, I was a little underwhelmed at the time I can’t remember the reason now, but think it was due to it being USA centric and the connection to Skydemon (my system of choice) not being reliable.

About the same approximate time, Pilotaware was starting out and the beta testers/builders were soldering up our own bridge boards (this was before bridge boards) using ARF boards.

I don’t know for sure which came first and I’m not sure it matters to me!

Fast forward 5 years and we have Pilotaware Rosseta and the Atom ground station network, providing uplinks from OGN and MLAT data from 360Radar. Skydemon even has Go Fly Pilotaware option too. No doubt this is the solution for use in Europe. Well, that was until the latest release of Stratux EU edition! The EU addition is a fork of the main Opensource project Stratux, it has been customised for use in Europe, dropping the UAT receiver and replacing it with an OGN and now Pilotaware receiver via one SDR, it has a second SDR for receiving transponders on 1090MHz.

Stratux EU

So Stratux EU is now receiving Transponders, Pilotaware and OGN traffic all directly on the device, not via a ground uplinks, for which you need to be in range of and no license fees either, although it has to be said the license fee for Pilotaware is very good value!

Below are some screenshots of Skydemon displaying traffic from the Stratux EU edition.

StratuxSkydemon

Choice

So which is better? that’s a very difficult question and not one I will answer, both have their good points.

First, if you want to buy a prebuilt and supported unit then you should look to buy a Pilotaware.

If you don’t mind not having direct support and like to play or know someone that likes to play, then maybe some of the Stratux features will win you over!

The user interface in Stratux is ahead of Pilotaware in my opinion, also you have features such as an AHRS, a better traffic list, G Meter and you are not reliant on ground stations to see gliders.

Pilotaware, however, is doing a lot to push the limits with their ATOM network, it also has a transmitter so if you don’t have a transponder it will make you visible to Pilotaware users and Stratux EU users too.

At the end of the day, I fly with Skydemon and both Pilotaware and Stratux show local traffic in Skydemon, both seem to have a reliable GPS and connection to Skydemon these days too!

Europa XS – The story of recovering a poor abandoned Europa part 3 (She flies)

Our Europa, she flies!

The wings were on and all we need to do was to weigh her and test-fly her “simples”! Andy was a little delayed due to flying over and not being able to get his aeroplane out of Turweston. I was watching out for him to arrive but missed him, he had landed and taxied up in a Eurostar before I spotted him.

Finding the datum in a Europa Tri Hi-Top was our first challenge, once we established this we levelled the aircraft using packing and established the centre line and the datums for the measuring of the C of G. Next we pulled her back up on the scales for the weighing. The surprising thing to me was that despite changing the battery for LiFePo4 and saving approximately 6Kg she weighed almost the same as she did at her last weighing, some 10 years ago! 

We needed to double sign the logbooks for the disturbed control surfaces, rudder and elevators that we had repaired and then we refitted. Even though this was taking longer then we expected all was progressing well. So we fuelled her back up and pushed her out before Andy did one last walk around before taking to the cockpit.

Flaps extended to take off settings and then the EFIS was switched on and… nothing! no lights no the EFIS. I went over to see what was up. The voltmeter was not reading any volts. It must be the new LiFePo4 battery! We had installed the new battery and done the 5 hot starts needed as well as operated the flaps and elevators a few times. The inbuilt battery management system had shut the battery off to protect against total discharge. 

Luckily the old battery was on hand and within the limits to refit for the test flight. We assume the new battery only had a holding charge and should have been charged before the test, or at least after it!

The old battery installed, she started on the button, this delay gave Simon time to arrive and witness the first take-off.

We have an airworthy aircraft, we now need to get our type conversion for the constant speed propeller and we will be off!

Thumbs up!

Europa XS – The story of recovering a poor abandoned Europa part 2

We left the story with our elevators and rudder sadly in the Europa factory shut due to Covid19. Since then the factor has partially reopened and our parts repaired and collected. Refitting them was straight forward (unlike the wings!). Although the engine started and ran well, as it had been stood for such a long time we decided to have a 200hr service and a check done, although we could have done this ourselves we decided to have a professional in. We use Gary Masters of Airmasters for our C42 Rotax so it made sense to have him look over the Europa’s 912ULS engine, even though his travel costs significantly added to the overall costs. Prior to his arrival we drained the fuel and replaced with fresh mogas (ordinary unleaded fuel to you and me).

Gary arrived on a sunny day in May and remarked on the fact that the Europa was one of the better examples he had seen. He advised having the pipes changed, but added that they looked OK, but were of unknown age, we declined this at this time, but will do it ourselves in the near future. He also said that the mechanical fuel pump should be changed as it was over 5 years old, this we agreed with and he duly changed it. The oil was very clean as was the filter, cylinder compression was near perfect, next he checked the gascolators these too were in good order. service completed time to start the engine!

Gascolator

The engine started first time and ran smoothly, the oil temperature didn’t increase, this was put down to the cold day and no cowlings, however we later found the oil sender lead off!

Engine serviced we tried to refit the wings but could not line them up with just two of us as neither had done this before, we decided to leave the refitting until the LAA inspector and Europa expert Andy Draper visits to do the permit inspection and to teach us a bit about the Europa. Andy used to work at Europa and is seen to be one the experts on them, we would be in safe hands.

On the day of the inspection, a number of minor things were found and we were able to fix these as they were pointed out. All was progressing well until we got to the point of refitting the wings! we were missing a rigging aid, but this was not essential.  With both wings on we could not get the port wing retention pip pin in, no matter how we tried and how we tried! The wings were removed and the problem examined. The rigging cup on the port wing had fallen off previously and we glued this back in place using Araldite 420 as advised. The rigging cup could only fit in one place as it sat in a fibreglass seat. Unbeknown to us the cup was about 0.5mm out of alignment and with both wings aligned this was enough to stop the pin going through.

This was adjusted the following day and the wing refitted, after a period of jiggling the wings the pin went in, it was still tight but we got it in!

The wings were finally back on and our Europa looks like an aeroplane once more.

Andy is due back to complete the inspection and to test fly her for the permit in the near future, I will update you all on how it goes.

to be continued…

Europa XS – The story of recovering a poor abandoned Europa part 1

Europa S
The drive home

A while ago myself and some friends decided to buy a GA aircraft, the criteria we set was a low wing, affordable (subjective, I know), Rotax powered aircraft. This effectively inferred a 2 seater, kit build, LAA registered aircraft. After we looked through the normal sites afors.co.uk, PlaneCheck.com, etc we concluded that a Europa fitted our requirement and we focused on trying to find an affordable Europa, it helps that the Europa Aircraft company is also only a short drive from where we live.

As luck would have it a hangar became available central to where we all live so we put our names down for the hangar and started the search for a Europa. This was somewhat frustrating as we had seen a few for sale before actively looking, but not many since. There was a Europa that had been listed for a while, but had not sold, so two of us made the 4 hour drive to view it. We quickly realised why she was still for sale as we looked around her. The current owner had made several modifications and not had them signed off, and although he seemed a nice guy, he was less than sold on the need to do so. The aircraft was on its third different engine type and bore the scars of the frequent changes in the form of holes in the bulkhead; fibreglass had been mounded high in placed to “add strength” the owner told us, It was a clear no from both of us.

I was sat at home the following evening feeling dejected at not being the proud owner of a Europa tri gear (we had ruled out the monowheel nicked named “the widow maker” enough said as to why!), when I decided to try and locate a Europa XS tri gear near us so we could go and look at one, talk to the owner and maybe, just maybe, cadge a flight in it! The only source of such information is Ginfo, I manage to identify 2 in the first page or so of results and then on the next page was one that caught my eye, it was listed as owned by Mr xxxxx for the estate of zzzzz. This sounded like and aircraft in probate! I Googled the owner, he was indeed dead, I Googled the other name and he was a solicitor, was this a tri gear? it was a tri gear, it was an XS and it had the wide and high mods too. First thing in the morning I call the solicitor, who was on holiday and referred me to another member of his practice. I called her and arranged to view the aircraft which at the time was at Popham airfield, within 2 days three of the group were on site looking at the Europa.

First impressions of the Europa XS

Europa S

We arrived at Popham airfield and waited in the clubhouse for the airfield manage to show us the aircraft. As he walked us over we were given a brief history. There looking somewhat sad in the corner of a field was the Europa XS that we had come to view. No keys were available, but the cockpit was unlocked on one side, so we climbed in and had a good look, one of the first things that struck us was how much more room there was compared to the Europa Classic we had viewed. The aircraft has not been flown or started in around 18 months, there was some mould on the stick gator, the rudder had been damaged assumably from a gust of wind causing it to hit the elevator, one elevator had delaminated on its trailing edge due to having been hit down on to a pole and both elevators had a mound of fibreglass near the release pins. overall she looked like a nice aircraft, the paintwork was bright, where there was no mould the interior was watertight and clean, still it would be a big gamble as we could not start the engine! We took the cowling off and burped the engine successfully the oil looked clean and free from water. On the drive home, there was much debate about the risk of buying an out of permit aircraft, especially one that had not even been started in 18 months, but we decided we would put an offer in that reflected this. We waited to see if we were successful or not, as we knew there were at least 2 other bids! After around a week we heard from the solicitor that our bid had been successful. 

The recovery  

Stripped
Loading
Still towing the Europa

We pick the first day that snowed in 2020 to go and bring her home, just our luck. Two set off for Popham and two set off to pick up the trailer. Simon and I arrived at Popham and started to remove the wings and the elevators ready for transportation. The guys with the trailed turned up, after taking a slight detour en route, and we loaded the Europa up and then started the long journey home. Our new home airfield was closed by the time we arrived, I think its fair to say we got some odd looks from the drives of the few cars that came around the corner to find a man waving a red flashing light and an aeroplane parked in the middle of the road!  We finally got the gates opened and pulled in and unloaded our Europa, she was safely stored out of the wind at the back in a dry hanger behind a Cessna 172 and a Piper Super Cub.

A few days later our faith in our purchases was validated by the engine starting first time after being stood for so long, the avionics sprung to life too, we had not wasted our money, a great feeling of relief was felt as she sprung into life!

Currently, we are all in lockdown and this has delayed the repairs to the rudder and elevators which sit in an empty Europa factory awaiting repair and the wings sadly remain detached too.

To be continued…

Radio interference can come in many forms, this is the story of two sources and how we fixed them.

Ferrite Choke

Recently our group fitted a Pilotaware with external antennas and at the same time we had the elevators and rudder re-skinned. Is the re-skinning unrelated, possible!

 

Sometime ago an LED strobe from Smooth aviation was fitted to replace the dead bottle flash and we had no noise from it. However, one of our group had reported intermittently hearing noise that seemed in sync with the strobe flashes. Smooth recommended cabling strobes is shielded Tefzel or similar. We fitted the LED strobe to the existing twin core flat cable (not shielded or twisted).

The aircraft also had an issue many C42A’s have,  in that when the PTT is pushed the trim indicator and the fuel gauge read erratically.

The buck converter used to power the Pilotaware was the second source of interference. This was the same type used for the GPS which had a low RFI (Radio Frequency Interference) footprint, however we are driving this one at around 50% of its capability and it was wiping out the intercom as soon as it was switched on.

So how did we go about isolating the source and fixing them?

First the strobe, the strobe noise was thought to be due to having moved the trim wire when we refitted the elevators and when we moved the strobe wire the noise would reduce and intermittently disappear. Thus, I deduced it was RF pick up issue and I moved the wire until we had continuous noise. Then I tried fitting a Ferrite choke at the strobe, this instantly cleared the noise, however the choke would not fit inside the vertical stabiliser. I tried fitting the choke in the fuselage between the last antenna and the tail, clamping it around the strobe cable, again instant silence on the intercom! To stop the choke moving I placed a cable tie either side and another around its body to act as a backup to the inbuilt clips.

Fitting this choke had the additional effect of removing the noise causing the trim indicator and fuel gauge being erratic while the PTT is pressed, the cable was acting as a pickup for any RFI

Ferrite Choke
Ferrite Choke

Eradicating the second source of interference

 

I then turned my attention to the Pilotaware buck converter, these are often noisy, but this one had proven to be OK in a low current operation, so I was not expecting this issue! Adding the choke was not expected to work on this noise source and it didn’t. I also tried creating a Faraday’s cage around it using tin foil, this worked to some degree, but was unreliable. Buck converters are notoriously noisy devices and the normally accepted way or silencing them is to fit an LC filter on the input (not the output) side. These are often fitted in radio control models to quieten down the ESCs (Electronic Speed Controller).

With this in mind I tried fitting a capacitor, the C of the LC filter, across the input of the buck converter and the noise was eradicated.

Noise suppression capacitors and ferrite chokes are two stand ways to remove or reduce interference, other approaches include, shielding the impacted instrument or the source of interference or using twisted pair cabling among others.

I hope the above helps others achieve a quiet radio in the aircraft, but if you are unsure about what you are doing, I would suggest contacting someone that understands interference suppression techniques to help!  

 

Ground plane sizing for radio, transponder and PilotAware

Transponder, radio and PilotAware antenna fitting in a non-metallic skinned aircraft

There is often talk around the hangers about poor radio signals and how some aircraft can be heard from great distances while other fail to make contact with a ground station even nearby. One of the issues often overlooked is a missing or wrongly sizes ground plane. There are many myths about the purpose of a ground plane and I hope in this short article to give you guidance on the correct size and purpose of a ground plane.

Before we look at the ground plane lets set expectation on maximum distance you can be heard.

The civil air band radio is in the VHF (Very High Frequency) band and under normal weather / tropospheric conditions, it requires radio line of sight between the aircraft and the ground station; thus, the maximum range is the distances to the radio horizon from the aircraft to the ground station, for simplification we are assuming the ground station is at sea level.

The radio horizon distance is given by the formula: D= K√h

Where: D = distance in nautical miles (NM), h = height of aircraft’s antenna above ground level and K = 1.23 when h is expressed in feet

So, when we are flying at 2,000ft the maximum range to a sea level ground station is 55.00NM or at 3,000ft 67.34NM

The same is true for transponders, CAP1391 devices e.g. SkyEcho and PilotAware transmissions, however the limited power and antenna arrangement of CAP1391 and PilotAware means the range is less.

What is a ground plane is and why we need one?

Keeping this simple, it provides a ¼ wave monopole antenna (also know as a Marconi) with its required counterpart allowing the flow of the electrical current which generates the electrical and magnetic waves that make up the RF signal. The earth acts as a type of electrical “mirror,” effectively providing the other quarter wavelength making it equivalent to a vertical dipole. This in turn helps present the correct impedance to the transmitter, thus allowing the maximum power transfer into the antenna, which results in the most efficient transmission of the signal. Most antennas sold for Microlights and light aircraft are ¼ wave.

Ground plane

Does size matter? 

I’m afraid the answer is yes it does! Bigger is generally better, but again there are exceptions and a minimum size for the efficient working. The minimum size is a radius of ¼ the wave length of the signal being transmitted.  In basic RF theory we were taught that bigger is better, although the benefits of size are less important above 3 times the wave length. In aviation while we are flying along we want our signal to be picked up both above and below the aircraft, the larger the ground plane the bigger the blind spot we will have on the underside of the ground plane.

Is the shape important? 

No, a ground planes can be square, circular or many different shapes. Say you had a metal aeroplane, the whole fuselage is the ground plane for your radio antenna, and your transponder antenna. So long as you have at least ¼ wave length in all directions, then the shape doesn’t matter too much. However as we want the lightest ground plane we can get, a circle is the optimum shape and supports equal propagation of the signal in all directions.

What should the thickness of the ground plane be? 

Any, you can use foil tape or discs of different thicknesses so long as it is mechanically robust enough and conductive.

Can it be a mesh or does it have to be solid? 

It can be a mesh (the tighter the mesh the better) or even multiple radial wires, typically the more the better 8 or 16, but for our purposes a solid circle is normally the easiest and best option.

What should it be made of? 

Copper, however it can be any material which is a good conductor. Aluminium is a good conductor and can be used, however you need to be mindful of the galvanic effect between a stainless-steel antenna and the ground plane. This may lead to connection issues in the future, thus I would recommend a thin copper disc.

Why do some avionics companies state to use a square ground plane? 

Well I assume this is just convenience, so long as the diameter of the circle below can fit within the square it will work fine. Just make sure the antenna is in the middle!

What does all of this mean in practice? 

Minimum diameter of ground planes in aviation should be:

N.B. Always round the ground plane size up not down.

Transponder: frequency 1090MHz, Wave length 275mm, ¼ wave length 68.75mm

Minimum ground plane diameter 137.5mm

Radio: lowest frequency 108MHz, Wave length 2775.85mm, ¼ wave length 693.96mm

Minimum ground plane diameter 1,387.9mm

PilotAware: external antenna fitting, frequency 869.5MHz, Wave length 344.79mm, ¼ wave length 86.19mm

Minimum ground plane diameter 172.39mm

 

Antenna Theory Is Complicated

Antenna theory is complicated, but if you have a ground plane with the correct minimum size and the antenna mounted in the middle this will be one less problem.  But let’s quickly prove this is fact and not just some text book exercise. As an extreme lets consider an antenna without a ground plane vs the same antenna with a correctly sized ground plane.

An external PilotAware antenna without a ground plane is put under test using a low cost VNA (Vector Network Analyser) 

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.

As can be seen opposite the resonant frequency of this antenna is not 869.5MHz as it should be! It is showing a resonant of over 1GHz. The impedance and VSWR for the antenna was also way out, in fact the reflections from the imbalance could damage the transmitter or at best the radiated signal will not be optimal.

Let’s add a make shift ground plane out of kitchen foil of the recommended size above.

opposite you can see the effect of adding the ground plane. The resonant frequency has shifted down to be close to the 869.5MHZ that we are looking for, the VSWR was down to acceptable limits and the impedance was close to 50 ohms.

Hopefully this graphically demonstrates the importance of having a correctly sized ground plane!

 

One last Fact! The monopole antenna was invented in 1895 by radio pioneer Guglielmo Marconi

Changing from Neuform to Kiev Propeller on an Ikarus C42A

This is a reflection of how I went about changing the propeller, it is not meant as a "how to" and no liability will be taken form any issue others may have by following this post!

We made the decision to change the original Neuform Propeller after noticing some hairline cracks across the back of the prop. This together with an accumulation of small chips meant  it was highly unlikely to pass a factory inspection, thus the prudent thing to do was to change the prop. 

Neuform Props are very good, but expensive props, so we chose to replace it with a Kiev which at the time of writing was around £1,000 less.

The first stage is to remove the top cowling, we also later removed the bottom one too, to allow us to have a good look around at the same time. This proved to be a prudent thing to do as we found our radiator bracket was broken too!

Next remove the spinner, a tip here which some may not know, is to hold the allen key bolt and undo the nyloc nut with the spanner, else you may start to round the allen key head.

NB: I found out the hard way, that you should mark the back of the spinner plate and the flange to ensure the spinner goes back on in the correct position!

Now we need  to remove the old prop by undoing the six M8 retaining bolts. These are the long ones which screw through into the flange.

After these are removed the propeller will come off still clamped in the hub.

The prop with its adaptor plate is now removed.

 

Removing the the lugs

Now for the  “fun” part, removing the lugs from the flange.

The lugs are used by both Neuform and Warp drive props, but not by Kiev props.

These lugs are press fit and difficult to remove. First spray them with AC50 and then  have a cup of tea while this goes to work!

The best way we found to remove them safely  is to use an M8 bolt through a 17mm socket, this acts a puller and pulls the lugs back through the flange plate without damage or shocking the gearbox.

Once they are almost through they will easily tap out.,

Fitting the new prop

First lay the prop out and loosely clamp the prop blades in the hub. Ensure the key marks are aligned (see image) this is just tight enough to hold it all together, while we loosely bolt the prop on to the flange using the new adaptor. Note the new adaptor plate can only be purchased from TLAC  and was around £120.00 inc VAT.

The bolts to hold the prop on are 110mm long if you purchase the correct ones. However  using these bolts mean they have 25mm of thread and about 12mm of this thread is  within the flange plate holes. This is not good engineering practice and after checking with the BMAA they agreed. The solution is to buy the next size up (120mm) and cut them down by 10mm thus giving 15mm of thread which means you will have about 3 threads out of the Nyloc and much less thread within the flange.

The bolts we used are M8 grade 8.8, DIN 931 120mm, cut to 110mm.

Once the prop is mounted and all the bolts are in, but not tight, they should be loose enough to allow the blades to be turned within the hub, but tight enough to stop them moving to easily.

Now the pitch can be set. We have found mounting the the pitch tool 48.5cm in from the tip on the inside of the mark and setting a pitch of 25 degrees gives the correct revs, 4,800 rpm on the ground. this TLAC confirm to be the correct test that the prop is pitched correctly. 

Work your way around all the blades in turn setting the pitch.

Carefully do the bolts up working your way around the opposite  bolts that clamp the blades first.  These should be be done up to a torque of 15Nm. Now before doing up the main bolts recheck, loosen and adjust and re tighten as needed the pitch for each blade. 

Lastly do up the mounting bolts that go through the flange, again do this progressively working across the opposites, these are torqued up to 25Nm,  then once again check the pitch and adjust the pitch if needed.

All that is left is to ground run the aircraft. Check your static full power rpm is 4,800 rpm +/- 50 rpm, our brakes don’t hold at this power so we check that we get this during the takeoff.

The torque of all the bolts need to be checked at 1hr, 25hrs and 50hrs after fitting the new prop.

I hope this has will help others, even if it doesn’t it will serve as reminder to myself if I have to do a third prop conversion!

Lastly you will need a BMAA inspector to sign your change of information form.

CHANGE OF DATA FOR A BMAA AIRCRAFT 

The little things count too when doing a preflight check!

Today we planned to fly to Le Touquet, but the weather had other ideas! As we could not fly to Le Touquet we decided to try Sandown, Isle Of Wight.

We started by cancelling the flight plans filled via Skydemon and then we set off. Initially, the cloud base was around 800ft but, soon and as indicated, this opened up and we climbed to 2,000ft and then 3,000ft as it continued to improve.

The flight down apart from the claggy start was largely uneventful. We had been having issues with our Funke TRT800 transponder, it is intermittently not being seen by ATC and locking up, however on the flight down it behaved impeccably. The only issue we had on the way down was the landing, I touched down gently and then hit a bump and a gust of wind which saw us back in the air, but not by much. Next, another gust just as we were touching down and 90 degrees to the runway saw our right wing lift. I caught this on the stick and controlled it with the aileron. I was wondering if I could have done better as I watched Colin land behind us in his C42 and saw him have the same issue, it was like watching an action replay however, this time the gust had taken him far to the left of the runway.

Approaching IoW overhead Portsmouth

The journey home, however, was much more eventful!

Funke TRT800
Tape causing the issue

First, the Transponder didn’t seem to be working, so we called Fanbourgh Information and asked for a transponder check, we tried Ident and they could not locate us, we tried another squawk but, we could not change it, so we need to send it back to Funke for a service repair.

About 40 mins from Chatteris we heard a loud ripping sound, it was like someone ripping velcro apart in our ear! followed by a humming sound! we looked at each other in disbelief, the aircraft was still flying and the controls responding normally. The humming stopped and all seemed normal so we decided to continue, and then another loud ripping sound more humming and heavy vibration through the stick and pedals!

What could this be? what should we do?

We looked for an alternative and near airfield, our best option was Old Warden so we head towards it, then as suddenly as it started, it stopped, we continued towards Old Warden with no further occurrence of the issues.

What could it be? Our best guess was that the velcro fastening between the wing and the aileron may have separated and the noise and vibration were due to the resulting airflow between them.

On to Chatteris and 10 miles out we heard Skydive One (the parachute plane) called it was taking off, wanting to get straight in we called Skydive one and advised them of our situation and they delayed the drop until we had landed. On final we put the first stage of the flap on, as the aircraft’s pitch changed the vibration and humming returned, we decided not to put the second stage on. After landing we inspected the aircraft looking closely at the ailerons and the skins, nothing! Then we spotted the windscreen tape had lifted in the middle of the vertical section, could this have been the issue? it would make sense re the ripping sound, but what about the humming and vibrations? we reasoned that the humming could also be due to this and possible the vibrations too if it was disturbing the airflow. The tape was removed and we took her up for a test flight and to our surprise, the issue was solved!

This reminded me of Rob Mott’s article in Microlight flying magazine where he talks about knowing your aircraft and not to panic if you have an issue. We knew the aircraft was still flying, we knew it was responding normally to all control inputs so we minimised the issue by flying conservatively and landing at Chatteris as soon as possible.

Little things like the edge of the tape lifting are important to check on a pre-flight check as well as the major items!. 

Should we have performed a precautionary landing?

We could have put her down in a field or at Old Warden, but she seemed to be flying OK and what damage might have been done during the landing? Old Warden is PPR and was NOTAM’d for model flying.

There has been some discussion if we were right to have continued flying or not. What is your view?