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?