Saturday, 28 April 2018

Titanium Firewall Part II

Once I finally got the engine back, I decided to make a firewall template out of coroplast before drilling my new titanium firewall (thanks to my friend Mathieu Gratton for the idea!).


This allowed me to try different hole locations and converge on routings for hoses, controls and wires that I was happy with. Took a lot of notes directly on the template for me to remember all details as I was trying each setup. 


I used the green tape on the coroplast to mark the location of the structural members of the fuselage. This helped to avoid holes or nutplates at a wrong location!

For the most critical elements like throttle and mixture cable holes, I placed the engine  as close as possible to its final location (the engine leveler helped a lot for that):



After taking some time to look at all this I decided to relocate the starter solenoid as well as the voltage regulator which were both mounted on the firewall before. The battery being behind the seat, it makes more sense to have the unprotected cable between the battery and starter solenoid as short as possible (I don't have a master solenoid). Also, after looking at specs from B&C aero, it is generally recommended to locate the voltage regulator behind the firewall for cooling reasons.

Once I figured out where I wanted all holes to be drilled, I transferred the final markings to the titanium firewall and drilled all I could using the press drill. Obviously some holes were too far from the edge so had to use a hand drill for these. Most of the holes were easy to drill with cobalt bits. The larger diameter holes were more of a challenge. Biggest hole was 1.0 inch. I used a unibit but it required patience since titanium is quite hard. Clamping the Ti sheet to a thick piece of wood helped. I also used cutting oil between each step and reduced the drill rpm as the hole was gradually getting bigger. Slowly but surely, I finally got there.

Last step was to install the nutplates. I also decided to rivet reinforcing brackets at two locations where more stiffness was required: behind the 802 oil valve and behind the brake fluid reservoir. I used a C-frame to make dimples and riveting (thanks to my friend Scott!)

As a comparison, here is the old SS firewall a.k.a. swiss cheese firewall:


Here's the wannabe firewall:


...and the final result:


Much less of a swiss cheese now : ) Next step is the engine installation!

Monday, 16 April 2018

Titanium Firewall Part I

While the engine was gone last year, I decided to take the opportunity to make a new firewall since the old one had many unused holes that were plugged. In fact it looked more like a slice of swiss cheese rather than a firewall.

The old material was a 0.025" thick sheet of stainless steel. When browsing on the biplane forum, I saw that some builders were using titanium to save weight! Since my airplane is a little nose heavy, switching to Titanium was killing two birds with one stone.

In order to select the material thickness, some guidance exists under FAA 14 CFR 23.1191 which says:

(h) The following materials may be used in firewalls or shrouds without being tested as required by this section:

[...]

(6) Titanium sheet, 0.016 inch thick.

I therefore proceeded an ordered a sheet of 0.016" thick titanium from Titanium Joe. Great service and quick shipping. First impression: ok Titanium is VERY light.

I used the shape of the old firewall to draw and cut the titanium sheet to the desired shape. I cut the biggest parts on a heavy duty straight shear and cut to final shape with curves using a shear similar to this:

Image result for metal shear

Then I drilled the holes for the aluminum frame rivets them using a cobalt drill bit and the old firewall:


When looking at my neighbour Luc with his Pitts S-2C, I realized the lower edge of his firewall was actually bent with a large radius in order to reduce air restriction and make it easier for the warm air to get out of out of the cowl. My old setup had a sharp edge corner which obviously created a lot of turbulence and air restriction. I didn't especially had oil temperature or cylinder temperature problems, but since I may relocate my oil cooler eventually, I thought I was putting all chances on my side to make a large radius bend like on the S-2C. Easier to block air down the road rather than to unrestrict it!

In order to block the gap between the radius and the flat adjacent areas, I had to make small brackets using the leftover titanium:


Here is the result after the aluminium frame was transferred to the titanium firewall and the work on the bottom edge complete:


Next step was to locate and drill the required holes. I didn't want to blindly copy/paste the old hole locations so I prefered to wait until the engine was back before proceeding... To be continued!

Tuesday, 26 December 2017

News from the engine shop

It's been a long time since I wanted to write this update and the Christmas holidays is perfect for it : )

The main symptom my engine had was typical: corroded lifters and cam lobes. Two lifters were definitely not airworthy:



The source of the metal found in the filter was mainly from the lifters. When reading this article about lifter destruction stages, it is pretty evident that these were in stage #3 and had to be replaced.

Since the cam was not in good shape neither, it also had to be changed. Took the opportunity to switch to a high performance cam (different lobe shapes that modify the lift and duration to optimize valve timing and increases combustion efficiency)

This engine only has 500h since new. The cylinders were inspected at the shop and were found in good condition so it was worth taking this opportunity to proceed with porting/polishing of their induction and exhaust tracts as well as carry out a flow balancing on them. This allows a higher volume, to flow with greater efficiency to and from the combustion chamber, hence producing more power.

While the cylinders were getting ported, the crankcase and oil sump got completely cleaned and painted:


The reassembly was also initiated:


Once the cylinders were back, they went for honing, but this revealed an unpleasant surprise: the inside of the cylinder walls were also affected by corrosion:


The solution for this was to oversize the cylinders by 0.010". This howevers means new, oversized pistons and rings. Here's a shot with the cylinders painted and the new pistons followed by pictures of the final assembly:





























Once the final assembly was done, the engine got installed on a test bench with a dyno. They ran it for a few hours and checked twice the oil filter for metal. Thank God nothing was found this time! Testing on site is is nice because the break-in of the engine is actually done at the shop. Dyno results were also interesting: with the high performance cam and ported cylinders, the engine produces about 10% more power at 2700 rpm.

The engine is still in the shop of Aerorecip in Winnipeg; it will be shipped right after the new year! Been working on a new firewall in the meantime which is going to be the topic of my next post.

Happy holidays to all of you my readers! I hope 2018 will be full of happiness and interesting projects for you!

Sunday, 15 October 2017

Metal in the oil filter

Yes, you read the title right.

In August, shortly after the return from the Green Mountain Aerobatic Contest in Springfield Vermont, I made an oil change since my oil was 4 months old (per Lycoming Service Bulletin No. 480). The engine total time since new was a little more than 500 hours. The oil had 25 hours on it and the oil filter 40 hours.

I have a B&C spin-on filter adapter that allows me to use a 48108 paper filter. I like it since it provides better filtering and allows to change oil every 50 hours instead of 25 hours when using a screen filter (especially useful in summer when flying a lot).

In order to inspect my old filter, I used the "blue rag" technique recommended by this EAA video. When cutting the filter open, I didn't see any big particles with naked eye. However, when I collected all the content of the filter together, I found about 1/8th teaspoon of ferrous metal powder:


Following this finding, I wanted to know what are the typical recommendations for this quantity of metal. Lycoming Service Instruction 1492 has info on recommended actions when finding metal in the oil filter. When reading this SI, I concluded category 8 d. was the closest to my situation:

"As in step b., but larger amount, such as 45-60 small pieces – change oil filter and clean suction
screen, drain oil, and refill. Run engine on ground for 20-30 minutes. Inspect oil filter suction
screen. If clean, fly aircraft for 1 to 2 hours and again inspect oil filter/suction screen. If clean,
inspect oil filter/suction screen after 10 hours of engine operation."

The step b. in question mentions:

"10 to 20 small (1/16 inch diameter or less) pieces of shiny flake-like, nonmagnetic, or 10 or
fewer short hair-like pieces of magnetic material"

The particles were all magnetic and way smaller than 1/16". Stricly speaking, they were not "hair like", but I didn't find a description in this service instruction that fitted better my situation. The generic recommendation from Lycoming is therefore to continue flying "on condition".

The following factors specific to my situation were also worth consideration:
  1. The engine was manufactured in 1979 and has never been opened since new. If it had flown consistently 1 hour every month since new, corrosion wouldn't be too much of a worry, but obviously it is not the case. Lycoming cams and lifters are know to be subject to corrosion if not operating for extended periods of time.
  2. The situation will not improve by itself. It can only get worse. More particles like this means more chances of getting into other parts of the engine and making more damage.
  3. This engine is in a Pitts. Lycoming's recommendation applies also on a Cessna 152, but I think nobody would argue that the severity level of an engine failure on a Pitts is more hazardous.
...so in light of all the above factors and recommendations...



Yes, I know. The bullet is getting pretty chewed up, but here I am. Season is over after only 15 hours of flying : ( It was a very intense 15h though and I enjoyed every second of it. I'm already anxious to put a nice, clean engine back in and go fly next season.

Thanks to Mathieu who helped in crating up the engine. Big thanks also to François Marquis, Kevin Horton, Mike Busch and JP Ouellette who all were of great help in gathering the pieces of the puzzle to make my decision.

Here's a shot of the engine just before getting shipped to Aerorecip in Winnipeg:


Next post will be on the findings from the shop... Stay tuned!









Tuesday, 29 August 2017

Some Flying!

Following first flight, I have been flying quite a bit. Getting back into pilot mode is a blast! Each second of practicing landings as well as aerobatic figures in this finely balaced aircraft is exquisite. The hard work on the rebuild was totally worth it.

Before the rebuild, my partner Luc and I used to have a routine after our respective aerobatic practices: perform 5-6 tight circuits together at our home airport. Durign the rebuild, we both dreamed about getting back into this routine together. We could finally do it!! What a feeling. Thanks Luc! We also went to the Green Mountain Aerobatic Contest together. François, a friend of us took great pictures:





Thanks to all IAC 35 team that organised this great contest!

Not too long after getting back from the contest, I found a unpleasant surprise under the cowling. Will dedicate another post on this...


Thursday, 25 May 2017

The great day I flew again for the first time

After lonnng weeks of waiting for suitable weather, I finally saw a sun pictogram in the local forecast. It was a Tuesday and it was going to be sunny, fresh, with calm winds; just perfect. Took a day off to make sure I wasn't rushing for daylight after work. I wanted to take my time to make sure both myself and the machine were ready. Moreover, week-ends here in Lachute airport can get quite busy, so it was worth shooting for a week day to avoid too much airplanes in the pattern.

I spent the night before doing a thorough walkaround, checked fuel, oil, tire pressure, and plugged the battery on trickle charge overnight. I started feeling the rush as I finished preparing the airplane and closed the hangar door that night.

Morning air was fresh, with a clear blue sky. Winds were calm and forecasted to pick up slightly during the day, but along the runway axis. Took the time to refresh my memory on the key items noted during the flight I did with my friend Luc in his S-2C the week before e.g. the things to remember, common mistakes to avoid, etc. The plan was to perform braking tests during taxi, run-up, then take-off and climb at 100 mph along runway axis until 2000 ft then turn-around while continuing the climb until 3000 ft which is the limit of the airspace. Then I was going to check engine parameters upright + inverted as well as stall characteristics.

Didn't put the wheelpants for first flight to ease post-flight inspection of the brakes. The taxi tests went well. Brake pedals were not spongy at all. After a couple of S turns and brake tests, the engine began sounding a little different, similar to plug fouling. After a run-up and a higher power run on the runway, it didn't improve much so I decided to turn back and inspect + clean the plugs. Turned out #2 cylinder plugs were quite dark indicating a rich mixture. This was in accordance to a flow divider test I did a few weeks before. I therefore decided to install a smaller restrictor to the #2 injector (Airflow Performance).  I also adjusted the idle mixture, cleaned the plugs and fit the cowl back on. Turned out it got improved so I taxied pyaing extra care about the mixture, did another run-up, took off and sticked to the plan. Although I was concentrating on what I had to do, the back of my mind was exhilarated by the acceleration feeling on the runway, especially the first few seconds in the air. Once at 3000ft, checked oil temp, oil pressure upright/inverted, fuel pressure upright/inverted with/without boost pump, checked CHTs and all was in-line with expectations. Did a mag check and got a few subtle backfires on RH mag that immediately disappeared when I switched to LH or both. This turned out to be my only snag. All the rest, including stall characteristics and hands off trim were surprisingly good. 

Just like the WW1 fighters, I looked down waiting for the perfect opportunity to dive and join the pattern. Carried a little extra speed in the approach to ensure good control authority all the way down to the flare. Plan was to do a full stop unless otherwise required. Landing the airplane after all this time felt amazing. 32 min flight total, 1 snag BNF (like they say in flight test: to be fixed Before Next Flight). Mission accomplished!

I remember when I almost had a syncope as I was preparing for the 2015 season. It was then the beginning of a looonnnng project...  Two years of work in total, little by little, spending evenings after work and week-ends at the hangar. I would be lying if I said that there was no phase of discouragement, but thanks to the help of my family and friends, and to you readers of my blog, I finally got back in the air with this little biplane so enjoyable to fly. When I think back of this first flight, the feeling of being at the controls of an airplane that I completely assembled was very peculiar, as if I was feeling all the small mechanisms moving behind each of my movements.

I want to thank my girlfriend Isabelle: you encouraged me all along, helped during the reassembly and supported my many days of absence, thank you! My father Victor for the important help during key stages of the reconstruction: engine and wings reinstallation as well as your help for the preparation of the first engine start and the first flight. Thanks to my mother Danielle for encouraging me relentlessly. Francois Marquis for countless technical advice at each stage of the reconstruction, and also for having supported the multiple, very educational words I pronounced on the phone when I realized what this crack meant. Thanks to Luc Martineau for keeping my morale up every time we crossed path at the hangar, for your help during the wing reinstallation, for your solid assistance during the first flight and especially for having supported my mess in the hangar during all this time. Thanks to Scott Black for the hundred tools I've borrowed from you and the many manufacturing tips and valuable references, as well as your help with W & B and parts machining, you were always there, ready to help. Thanks to Mark Clément for the excellent and precise welding work, your multiple trips to Lachute and your special care to understand what I needed. Thank you Paul Goyette for your precious time and your incredible attention to detail and patience that allowed me to make the trim tab and wing rigging tool. Thanks to Marc-Antoine for help in repairing the left wing attachment bracket, baffle, longeron brackets, as well as the many encouragement and our flights in the Citabria that helped me stay on tracks and fulfil my lack of vitamin G. Thanks to Jocelyn Côté for your patience, the multiple top quality parts refurbishments, and technical advice. Thanks to Mathieu Gratton for the great help in writing the logbook entry and mod report for the local authorities. Thanks to Raphael Langumier for your procurement help. Thanks to Francois Bougie for allowing me to visit the Pitts International Archives which got me crucial information for the repair. Thanks to Russ Larsen for helping with the final inspection and driving into crappy weather afterwards. Thanks to my friends from Wichita: Jeff Hyde for technical advice and very educational workshops at your hangar, Chuck Ellis for the unparalleled airmail service exclusive to aircraft building parts, Mark Wood for help with the fuel system redesign and the idea of ​​the siphon valve, Ben Van Kampen for great tech tips. Thanks to Wes Liu for sharing the idea of ​​split nosebowl attachment. Thanks to Dani for helping during wing reinstallation. Thanks to Francois Viau for help during the propeller reinstallation. Thanks to Peter Ashwood for the encouragements and information on the S-1T. Thanks to Bill on Biplane Forum for sharing the plans of the rigging boards. Thanks to Richard Perron for the multiple tool loans. Thanks to Pierre Bérichon for the loan of the shop crane which lasted a lot longer than expected. Thanks to Claude Camirand for the mag drill. Thanks to the team of Griffon Technical Services who have helped me several times. Thanks to Luc from BL Aviation for the quality service during the inspection of the magnetos. I'm deeply sorry if I forgot anybody and still thank you! I also want to thank again the readers of this blog; knowing that what I was writing wasn't too boring certainly helped keeping the momentum!

Thanks again to all of you that helped me throughout this long project. You made all the difference, both for technical and moral support. Each one of you made the dream to fly again in this airplane possible.

I will continue updating this blog with updates on my activities with my Pitts so feel free to come back now and then!

Cheers,

-Dimitri

L’image contient peut-être : 1 personne, ciel, plein air et nature


Monday, 8 May 2017

While the rain is falling - New hangar mezzanine

I plan to fly with my friend Luc in his S-2C to get back in the groove of flying a Pitts. However, Wx over the last two weeks in our area has not been suitable for flight; it rained so much that many places are flooded. We therefore took the opportunity of this crappy weather to work on an important improvement to the hangar: a mezzanine.

There wasn't even a toilet in the hangar before. In winter at -20°C outside, jettisoning your unusable fuel can be painful. This mezzanine has many important new features that will make the time spent in our Pitts stop more enjoyable:

  • Washroom
  • Hot water
  • Kitchen area with microwave, sink, small stove and fridge
  • More storage room
  • More light
  • Better sound
  • Dedicated spot for de-humidifier 
  • Clean area for flight preparation, documents and books
  • Security camera

Our friend Joe was kind enough to put our birds in his hangar free of dust for two weeks. Here is how our spot looked like before starting the work:



Initial structure work, very well done by Rich, the carpenter of the airport:



Bulk of the structure completed:


Working on the fence + table finishing. Note the ledge to minimize the risk of dropping something:


Epoxy coat:


Almost done:


Spent a lot of time to reorganize the storage:


Final shot, ready to roll the airplanes back in!



It was raining cats and dogs so we'll move the airplanes later : (

Big thanks to my friend Luc for the great initiative. It will definitely enhance the hangar experience. We can actually receive people now so if you come up in the area and stop in CSE4, feel free to drop me a line to meet us at our new Pitts stop!

Stay tuned for the next update on the Pitts : )