Wednesday, 24 May 2017

Propeller Dynamic Balance

On Monday I visited Gloucester Airport to get a Dynamic Balance done on the propeller by RGV Aviation.

I had been meaning to do this since getting the full permit but what really motivated me was a vibration which I didn't seem to remember when I first flew it. I put this down to being more familiar and picky with the aircraft the more I flew it - but as you will discover below I was not imagining it after all.

The procedure starts with the top cowling coming off first then two sensors are attached. One is measuring the RPM very accurately and does so by 'seeing' a reflective piece of tape which has been applied to one prop back face. The other sensor measures the vibration in Inches Per Second - IPS. This is mounted to the front of the engine as close to the prop as possible.

The engine is then run up to full static RPM - in this case 2700rpm (with the top cowl off I get 100 more rpm out of the engine as the air is colder going into the air filter).

When full static is achieved the ACES unit is set to measure the vibration which only takes about 5 seconds or so.

The first reading was 1.26 IPS - which is BAD!

Typically they try to get the IPS down to 0.07 or less. Adam the mechanic said the worst they have ever had was 1.6 IPS so mine was quite bad and the ACES machine called for a 45 gram correction weight which is beyond the 30 gram limit.

Another more senior mechanic came out to look at it and suggested to take the prop off and turn it through 180 degrees before fitting it again on the backplate.

So we did that and lo and behold the next reading was only 0.15 - which is nearly a 10 fold reduction in vibration! 

I think I must have had the prop this way round when I first installed it - then at the 15hr service I must have put it on the other way. There is no right way as such - theoretically the prop should be the same either way but it must be heavier on one side and this just happens to cancel out the vibration or accentuate it depending on which way round it is fitted.

The next 4 runs were done after putting test weights where the ACES machine told us to. And when the 2nd to last run came up with an IPS of 0.02 Adam was satisfied that we had nailed it. The final weight was then fitted permanently to the backplate and it was just 3.4 grams of correction needed. A final reading after that showed it back up to 0.07 so work stopped there. 0.07 is the figure they work to and Adam explained that the final weight is tricky to get in the right place to retain the IPS we had previously.

Anyway the proof was in the test flight back home - turbine smooth now compared to before. 

My wallet is now £300 lighter but this was well worth doing and I would recommend it. Not only is everything subject to less vibration but it is also much more relaxing to fly when things are smoother.

This also explains why I lost the cowling screws on my France trip as the extra vibration must have worked them loose.

Adam fitting the sensors.

Vibration sensor mounted to the front of the engine.

Both sensors in place - the yellow sensor taped on the plenum is the RPM sensor.

The ACES machine displaying the first reading after switching the prop around. As you can see it calculates a 'solution'. Which is a weight and degrees from datum to fit it.

A protractor is then used to figure out where to place the correcting weights.

A test correcting weight using one of the spinner holes.

The 4 readings after switching the prop around.

The final correcting weight - just 3.4 grams - consisting of a screw with a small washer and nyloc on the other side. BTW this is where the ACES machine said to put the final weight - it calculates the position taking into account you are not putting it in the same place where the test weights were put.



Saturday, 29 April 2017

Thursday, 27 April 2017

New camera position, aero entry speeds and maintenance matters

G-FUUN has done 50 hours already. So I'm doing the 50 hr maintenance now.

As an update to the 15 hr maintenance issue - the overly large amount of metal found in the oil filter. After sending the filter to Patrick at UL Power for analysis I changed the filter and oil again at 26 hours as a precaution and to see what would be in the filter this time. It turned out to be virtually clean - see below photos. Just one small ali flake and no steel.

I've just cut open the latest filter at 50 hrs and it is completely clean. So this is reassuring that the original filter just had to work very hard to remove all the swarf from the CNC machining in the factory. Clearly they had not washed all the swarf out before final assembly. The engine is not producing any more metal which bodes well.

During this latest maintenance I also noticed what I thought was oil on the pushrod tube of cylinder number 3 - See photo below. After further investigation it seemed to be coming from above the tube and dripping down onto it. So the pushrod tube itself is not leaking. I thought it may be the cylinder head gasket which was leaking. I sent this information to Patrick and his response is posted below:


Andy,
This is not oil but “black stuff” I think. We saw it several times.
Problem is a leak on the exhaust gasket. When engine do not run for a while , condensed water comes in the exhaust tube and even during first run ( starting the engine) condens coming from the sucked air is in the cyl head .
This “black” water comes out along the gasket and falls up the tubes. It looks as oil, but it isn’t.
So no problem in fact. You can try to re-torque the 4 bolts on the exhaust tube, or replace the seal.
It is for sure not the cylinder gasket.
Met vriendelijke groeten,
Cordialement,
Best Regards,
Patrick Denorme

So that's good news. I will try a re torque of the exhaust bolts and see if that helps. If not then I may try a new exhaust copper gasket on number 3.

UPDATE: Today I discovered that one of the exhaust flange screws was missing! That explains the leaking gasket and 'Black stuff' on the pushrod tube. This is not specifically mentioned in the maintenance manual as part of the inspections but I will be adding in a check of these screws from now on. I went round and tightened up all the rest - some of them were a bit loose. Beware - the lock washers do not really work.

After discussing aerobatics with Crispin I noticed that their flight manual had much lower entry speeds than what I had been using. Typically their speeds were 20 knots slower. 

After trying these new speeds the aero sequence is now much easier - no longer a tendency to accelerate too fast on the downlines of both the stall turn and the half cuban. Also the whole sequence now takes up less space so the danger of running outside the 'box' is much reduced.

The speeds they determined are as follows (all in knots):

Stall Turn - Entry 125 - Exit 125

Loop - Entry 110 to 125 - Exit 115 to 120 (the slower speed will produce a 'Granny' loop - so best to aim for 120-125 Entry and a 4 G pull).

Roll - Entry 100 to 125 - Exit same speed

Half Cuban - Entry 120 - Exit 125

Half Loop with Half Roll - Entry 130 (50 over the top then accelerate to 80 before doing the half roll)

Half Reverse Cuban - Entry 120 - Exit 120 to 130

Vertical Roll - Entry 135

Avalanche - Entry 130 - Flick Roll on top at 75

Outside Loop - Entry 130 - Exit 70

Rolling Circle - 120

I've also tried a new camera mount position - on the tailplane - which is giving a useful view for analysing my mistakes with the aero sequence. Only problem is the lens gets oiled up during the stall turn and the image then gets blurry. So I have just moved it to the right hand side tailplane and hopefully this will cure that problem. This view is of no use on the upline of a vertical though so I may supplement this with a wing view later.

The competition is just a month away from today so I need to up my practising schedule.


Only bit of ali from the 26 hr filter change. And no steel which is the main thing to worry about. The 50 hr filter is completely clean with no metal at all.

The whole filter from the 26 hr change. Click pic for much bigger view.
'Black stuff' from exhaust gasket. See UPDATE text above for the reason for this issue. 
New camera position on the tailplane. 

STOL Twister - airborne well before the numbers at Little G.



Florida Twister

It looks like the Florida Twister, built by Deborah and Richard Van Treuren, is nearly ready for its first flight.

The cowlings on it are the ones given to me by Matthias Strieker - as I ended up building my own cowlings I decided to donate them to this Twister project. Glad to see them being put to good use.

This Twister's resemblance to a WWII Naval fighter is because one day it may be the star of a film. The film is a fictional tale about an Airship that houses fighters in it's belly.

Powered by a standard UL Power engine - 97hp, not the high compression version, but plenty of grunt and you can run it on a lower octane MoGas too which is useful, swinging a Sensenich prop.

The plan is to meet up with the Van Treuren's in Oshkosh and park our Twisters next to each other. Should make for a nice photo.

Here's wishing them the best of luck with their first flight and testing programme.

My old cowling being put to good use. They have opted for a similar layout to the French Twister with the oil cooler in the nose. Below the oil cooler is a landing light.




The panel, complete with autopilot!

Wednesday, 19 April 2017

That's amore

https://www.youtube.com/watch?v=XHtdGJfVd2w

When you dance in the sky with a cloud way up high.

That's amore...


And when your kicks match your plane... that's amore too.


Electric Twister aEro and developments

I spent at least 2 hours talking with the H55 team about the electric Twister at Aero Friedrichshafen.

The team cannot be of a better pedigree as they are the same people who designed and built the Solar Impulse 2 - the round the world electric aircraft.

More details and specs on this site: 

http://www.hamiltonwatchaero.com/

One of the test pilots I was talking to (Dominique) said he thought the take off distance of the electric Twister was about half as much as a normal Jabiru powered Twister.

It also has a climb rate of 1,700fpm - this does not change with altitude either as the electric motor puts out the same power regardless of atmospheric pressure.

Currently it has a 100kW motor and they are planning on putting a 200kW motor in it next. This will give it a power to weight ratio about double that of an Extra 300.

Also they are building a new wing - which will use the same molds so the profile is unchanged - but there won't be any flaps. In their place will be full span ailerons giving a 400 degree roll rate! The outer wing tips will be 'clipped' too to further improve the roll rate (although this will destroy the Twister's beautiful lines).

Dominique said it is unlike any other aerobatic plane to fly in a sequence as the motor acts as a brake when you are going down (gaining energy as it does so with regen). So the sequence has less change of airspeeds and any downlines can be made longer.

He also said it is virtually vibrationless in flight "Turbine smooth" and with no noise other than the wind rushing past the canopy.

The price of the current electric motor is eye watering though - $100,000.

It only weighs 13kg - if you were happy to have a motor double that weight then the price would come to 1/5th of that - so $20,000.

Exciting times for electric aircraft.

The 200kW version with it's new wing will be a Twister 2.0



Woodcomp variable pitch prop helps performance.


Cut down gear leg fairings with massive gaps.

I think these two split inlets from the NACA duct underneath go to the batteries in the wings to provide air cooling.

Charging plug - takes 1 hour to charge.


NACA duct at the front of the cowl feeds air to the batteries mounted on the firewall - this duct  has an integrated rain separator, water and batteries don't mix well.

Inlet below the spinner is for the radiator that provides liquid cooling for the propulsion motor which is kept at 60 degrees C or below.

New wing being designed/made. No flaps and full span ailerons - aim is for 400 degrees roll rate. 4.44 times the current roll rate!

Interior is a bit spartan - not a lot of 'love' gone into this - however it is a proof of type prototype so that's forgivable.

Canopy restraint attachment and no headrest.

Pretty simple panel with this powerplant.

Transponder has been removed as it was causing interference with the battery controller.


Wednesday, 12 April 2017

Twister Touring

10 days, 5 countries, 1,595 Nautical Miles, 17.6 hours flown and 1 simply fantastic fuun filled flying holiday.

Lots of pics below will tell the story.

Suffice to say the Twister performed brilliantly - it's not such a bad little touring aircraft. 

Fuel burn was averaging out at 14.3 litres per hobbs hour. This is quite a bit less than the 17 litres per hour figure I had been told by Pete. I found out that he always cruises at max continuous - 2,800rpm. Whereas I found myself cruising at 2,680 - 2,700 most of the time. So despite the weight of G-FAAT and all the baggage we were still able to cruise at 125kts TAS at altitude and burn less fuel.

I had headwinds for pretty much the entire trip. The worst being 35 knots on the nose just after leaving Valreas Visan in Provence - the Mistral wind doing it's thing and funnelling down to the coast. I did get a small tailwind on the last bit of the last leg when heading north from London back to Little Gransden.

The only issues I had were minor.

I noticed that the bottom two cowling screws at the back worked loose - luckily I had already prepared a 'spares' kit and so was able to replace those. I then made it part of the pre-flight to go round and tighten up/check all the cowl screws each time. Weird this happened at all as it has not been an issue up to now despite being aerobated around the sky and cruised about at the same airspeeds.

The iPad got too hot in the direct sun over Switzerland and shut down. I put the screen near the air vent to cool it off and then shaded it from the sun with my left hand for the rest of the trip and it was not a problem again.

During some moderate turbulence my head hit the canopy. I was wearing a cap with a dome at the time and all the force was concentrated through that small area of the metal dome right on my head which made the air in the cockpit turn blue for a few minutes. After that flight I switched to the cap that Crispin lent me which had the dome removed. That's what I will wear from now on but am already planning a 5th point harness installation as I feel this is needed anyway for doing negative G aeros.

Onto the pics...



Passing London, Canary wharf and O2 dome.

Mid channel at 5,000 feet and I spotted this sub. It was followed by a Destroyer about 1 mile behind for protection as it is quite vulnerable when surfaced. Not sure which Navy it belonged to.

Approaching Le Touquet

Le Touquet. First stop for obligatory customs and a fuel top up. Parked next to the other G-reg there so he did not feel so lonely.

The Red Devils, Belgian display team, arrived shortly after in their SIAI Marchetti's.

Heading south, routing East of Paris here. The weather was like this the whole way down France.

The Loire river, France's longest river, winding it's way out to the coast.

A small diversion to overfly the famous Roman Aqueduct, Pont du Gard.

Finally arrived at Salon de Eyguieres.

The French Twister agents, Michel Sudre at left and my host Crispin Vincenti Brown on the right.

Michel takes me for a local sightseeing flight in his Pioneer 300.

Roman ruins.

Gliding field where the solo world endurance record was set in 1952. 56 hours, 15 mins. They used spot lights to light up the ridge at night and the glider soared back and forth on the constant Mistral wind that blew up the slopes of the ridge in this photo. (This record was broken in 1961 in Hawaii with a flight of 71 hours but that was not solo they had two pilots).

Michel and Crispins 2CVs.

Going for a wander around the airfield with Crispin and 2 of his dogs.

A nearly finished Twister in Crispins hangar.

Michel has made a great job of this cowling. Note the smoothed outlet area to the left - it is even curved on the inside edge.

One of many mods. The cabin air NACA inlet has been moved from the top to the side of the fuselage (to stop rain and any other debris from collecting in it.)

Non factory supplied fuel pumps. 
General overview of the underside.



A sensible mod - smoothing out the contact face of the gear leg 'knees' with flock. Makes for a larger and smoother contact area for the gear legs on their mounting points. I wish I'd done this!

Visiting the Musee de L'Aviation - a great little museum near Marseille Airport.

Michel was Chief Test engineer at Eurocopter before retiring. Here he studies the rotor head of a Super Frelon - a type he flew to China in.

Bristol Hercules engine being studied by Crispin and Michel.

The record setting AS350 Squirrel which landed on the summit of Mount Everest. Still the only helicopter to perform this feat.

We found a display with Michel's photo on it. Circled in red.

The speed record Eurocopter X3 - 255 knots!

This gizmo in the back of the X3 keeps the upper rotor and outboard props from vibrating out of phase. No idea how this works - looks more like the inside of the Tardis to me. 

Michel talks to his old boss from Eurocopters.

Not just any Mirage but the Mirage used to test the flight controls for the Concorde.

The simply amazing model room upstairs - I've never seen anything like it. It seemed to have every type of flying vehicle ever made - including space ships.

Half and hour flight north to Valreas Visan to spend 2 days with my Uncle and Aunty who live nearby. Nice little friendly airfield with fuel and hangarage.

Nuclear power station on the Rhone river. Do not overfly these or you will be shot down/fined 15,000 Euros - take your pick!

Lake Geneva, turning base for Lausanne my lunch stop on the way to Friedrichshafen.

Lunch in Lausanne. Good place to stop with usual Swiss excellence as part of the experience.

Staying away from the mountains in Switzerland - not a day with weather to fly over them.

Joining downwind for Friedrichshafen - Zeppelin approaching the airfield too.

"The pattern is full". 5 fixed wing waiting to take off and I am cleared to land while the Zeppelin goes over the top of me on the roll out. Lucky I didn't have to do a go around.

My accommodation for the next 3 nights. Tent City in Hall A2. Cheap and very convenient. Earplugs essential to avoid the snoring and other noise.

Hybrid amphibian from Norway. The very interesting Equator aircraft.

The electric Twister from Switzerland. Much more about this in another post coming soon.

Really taken with this. Tarragon. A German improved version of the Millenium Master/Blackshape Prime.

One piece wing of the Tarragon made from Prepreg Carbon with 150 degrees C resin.

Interior of the Tarragon.

Really neat little Rans S9 that has been modified - great little cheap aeros machine.

East European way of selling an aircraft. 
I've no idea what this display was about.


Having lunch with the Strieker brothers and Dornier's grandson (in the cap).


100th anniversary of the Zeppelin this year.

Exciting new twin rotor rotary engine. 100hp, 64kg installed weight, 12,000 Euros and would fit in a Twister! 
Lovely old Junkers with open cockpit.



Electric Pipistrel Taurus motorglider.

All ready to leave Friedrichshafen - perfect weather for flying.

Looking back over Lake Constance and the Swiss Alps. Dead smooth at 5,000ft above the inversion.

In the cruise over Germany - happy with these numbers.

SkyDemon is just a great app. Wouldn't want to fly without it.

Barges on the Rhine

Nurburgring racing circuit.

Nurburg Castle

The famous Carrousel on the Nordschleife Circuit. Ridden around here on my motorbike many years ago.
Happy man on arrival at Johan's local airfield, Zoersel/Oostmalle

Arrived in Belgium and the locals have this weird tradition of taking photos in strange locations with kids who have just been christened.

Twin Twisters. Johan parked up next to me.


A happy Johan with his Twister.

Panel layout is very similar to mine - happy to be of inspiration to him.




A nice formation flight in the evening. 
And again the next morning. Nice to be in the air with another Twister.
Quick stop at Brasschat - another local airfield.



Heading over the docks north of Antwerp. 

Beautiful Brugge

Calais was all closed up so I departed an hour earlier than my flight plan and had Lille Info change that in the air.

Mid channel and with many Belgian bugs on the windscreen.

Coasting in at Dover


SPOT Tracker trace of the route taken.