Shadrach

legally airworthy? Sure. It's the tax evasion that is the problem.

I’ve been thinking about this and it does not make sense to me and here is why. I have seen fluids more viscous than hydraulic fluid rapidly degassed befor they cure. A degassing chamber rapidly (necessary given the curing times) is used to remove large and fine bubbles from epoxy resins and silicone. It uses about 1 bar of vacuum to do so. The Epoxy and silicone are significantly more viscous than 5606. Why is it that you believe that hydraulic fluid cannot be degassed by applying one bar of vacuum to the system at the reservoir?

I cannot speak to the M20R but I can say that some of the vintage birds seem to have a high spot between the cylinder and the caliper when resting on the gear. I don't know that this is actually the case, but the sometimes stubborn pockets of air that are challenging to evacuate make it seem so. Rapidly pushing fluid up from the caliper seems to be the best way to drive it out of the system.

Mighty Vac was the last part of the process for me. I was able to get an acceptable amount of peddle just from driving fresh fluid from caliper to reservoir. Putting a vac on the reservoir just made it easy to get the remaining air out of the whole system. The brakes were relatively quick and easy from start to finish. After this last flush and fill, I came away confident that I had dialed the procedure for one man hydraulic system maintenance.

If debris is a concern, the system should be thoroughly flushed. I have never found debris in a an aircraft brake system. I have however found gelled fluid, and it would seem that it is easier to push it out using gravity to your advantage by pushing it out of the low point fresh fluid. This can be accomplished by actuating the brake cylinders with the bleed valve open. As for bleeding a flushed system, it seems counterintuitive to try to try to suck the lighter substance down through the heavier substance. In both of your scenarios you’re trying to suck or push the lighter of the two substances in the system, namely air, down and through the heavier substance, namely hydraulic fluid, and then out of the bottom of the caliper… A pressure pot placed at the caliper pushes fresh fluid in at the low point driving the air up an out through the reservoir. A vacuum on the reservoir creates a low pressure area at the high point providing additional encouragement for the air to move up and out and without sucking fluid into the pump. There may be applications where the process you describe is beneficial, but I can’t see how it would be beneficial for bleeding a Mooney (or most any other GA aircraft). The bleeding procedure in the factory MM is poorly written, but as I read it, it recommend pressure pot at the wheel and over flow tube at the reservoir. The mighty vac on the reservoir technique is mine own though I am sure others have come up with similar methods.

Did you mean Mighty Vac on the reservoir? I cannot imagine putting a vac at a low point in the system.

Farm diesel too! Years ago I knew of a guy in Northern PA that was running a Mig-17. It was rumored that operated almost exclusively on off road diesel. While illegal, I understand why at >200GPH burn rates. The running joke was that Ultra Low Sulphur, farm diesel was likely far more refined than anything the Soviets ever put in it.

This last time I did my brakes, I was alone. Knowing this would be a challenge, I employed the following procedure which worked flawlessly. Tools: Mighty Vac - This is simply a hand pump that draws air out of the system. This inexpensive pump from Harbor Freight or any other brake/clutch bleeder would work just as well. Motive Power Bleeder This is simply a pressure pot the pushes fluid into the system. Any other pressure bleeder would work as well. I have seen garden sprayers repurposed as pressure pots as well. 1/4" AN flare fitting for Hydraulic reservoir. Various fittings and several feet of vinyl tubing in different sizes. Various hose clamps or zip ties. Clean Bucket/Catch can Procedure: Flaps first - Make sure flap lever is in the up position. Attach 4' of clear vinyl tubing to flare side of 1/4" AN fitting and clamp to seal. This will serve as an overflow. Remove plug from fluid reservoir and and thread on AN fitting with tubing. Ensure tubing outlet is in a bucket/Catch can. Fill pressure pot with one qt of Hydraulic fluid. Royco 782 synthetic is superior to 5606 in my opinion. They can be combined if not fully draining the system. Attach pressure pot to the T fitting on the flap actuator with a clamp. This is the lowest point in the system. It is accessed though a small oval panel just ahead of the stub spar. It is a tight space with which to work. Make sure the pressure pot hose is well secured to the fitting and is not kinked. Pressurize pot (30-35PSI is plenty). Get into the plane and watch for fluid at the reservoir overflow tube. As soon as fluid is visible in the hose, begin pumping the flap handle vigorously. You should feel it pulling fluid into the pump cylinder. Exit plane and have actuator T fitting cover on hand. Depressurize pot, then quickly remove hose from T fitting and replace with cover. Clean up hands/remove gloves. Pump flaps do to lock out position and leave them there. Does not matter how many pumps it take at this point Using a straw as a thumb siphon, reduce the fluid reservoir to ~half full Empty catch can into pressure pot move on to the brakes Brakes - Attach pressure pot to bleed nipple on bottom of caliper and secure with clamp or zip tie. Pump pot to 30-35psi Open bleed nipple Get in the airplane and pump the appropriate peddle as fluid is pushed into the system. You will feel fluid enter the brake cylinder. When over flow is noted, get out of plane and close the bleed nipple. remove pressure from pot and disconnect from caliper. Repeat process on other brake circuit Using a straw as a thumb siphon, reduce the fluid reservoir to ~ half full Attach hand vacuum to reservoir. This can be done using the vent on the top of the reservoir or the fill opening; it does not matter which but the other will need to be blocked so it is air tight. Draw the system down to 20- 25inHg and position the pump so that the gauge can be seen from the cockpit Raise deployed flaps while system is under vacuum. Actuate flap handle (lever in up position) and brake peddles from cockpit while system is under vacuum. Release vacuum and test systems. Repeat if needed Remove pump, unblock reservoir vent and go fly. Notes: Not all hydraulic reservoirs are the same. Depending on year, some are welded aluminum cylinders with AN fittings and some look more like a repurposed solvent container. The person servicing the system will have to procure the correct fittings to work with the installed cylinder. Either flaps or brakes can be done independently without doing the other. I personally prefer to start with flaps when doing both. It may take a few days for all of the air to vacate the flap system. The best way to facilitate the process is to pump the flaps 3/4 down and leave them for a day (or a week). If a freshly rebuilt flap pump is being installed, fluid will travel more easily through the system with the retraction speed adjustment screw backed out to max flow. This is not necessary, but may make the process easier. Conversely, if the retraction screw is inadvertently tightened all the way down, fluid will not flow through the system. I welcome comments if it appears I have left anything out.

It is a PITA for first timers and sometimes seems to stump seasoned Mechanics as well. A lot of the time it boils down to not having the right tools for the job, sometimes there are assembly problems with a rebuilt pump (I've run into this twice in the last 6 months). However, I system that has had no maintenance other than a drain and flush should be fairly easy to return to service. The reason I suggested the vacuum hand pump is because it will eliminate air from almost all of the system pretty quickly. The exception being the pump cylinder, The last bit of any air trapped in the pump will have to work it's way out. I was not bragging, I was merely posting what is possible when one has the right tools and processes for the job. I was working alone and took the system from full of fluid, to full of air, to full of fluid in under two hours. It is not rocket science, but small details can impede success. If the flap pump has been removed and rebuilt, that adds another area of potential problem. In the last six months I have encountered two different aircraft that have had what seem to be improperly serviced flap pumps (both pumps serviced by MSCs, though I don't recall which) installed. Full disclosure, I was not on site for either situation. In one case the pump was returned to the MSC for warranty repair. Post warranty reinstallation went flawlessly. In the other, I sent them a pump that I had on the shelf and they were able to coble together a working pump by "Frankensteining" them together.

What kind of issues? I just did a drain and flush replacing the 5606 with Royco 782 Synthetic. I'd estimate it took me a little under two hours total from drain and flush then fill and bleed the flaps and brakes to completely solid. It's pretty straight forward. If he can't get all of the air out, he should consider putting a vacuum pump on the reservoir.

Most nose wheel aircraft are poorly configured for hand propping both in terms of prop index to compression stroke and the fact that engine sits lower when on a nose wheel. I once watched an old timer hand prop a twin Comanche in front of a restaurant. It looked so bad that I asked him to stop. He grumbled something like “thank you but mind your own business”. He got it started in two pulls, got in, started the second engine and departed. I thought for sure he was going to stumble right into the prop arc.

Yup and yet…they still get away sometimes.

Might have been me. Do you currently need one?

Why not chock both wheels? Rope is cheap. Having an extra long piece for the left chock makes it easy to pull without leaving the right side of the plane. I realize lots of folks chock just the right wheel. But if you miss set the throttle, the plane is going to pivot around and jump a single chock. I love Martha Lunken’s writing. However it is clear that she came up in a different era of aviation. She has had some incidents that have left me thinking that she’s exercising the kind of decision making that would have been mainstream in say, 1971.

I would not assume TSMOH alone is the culprit. I had to fabricate some cowl flap hinges or I would have been out collecting data this weekend.

Allen, I am very impressed with the prototype and your development methodology. Thank you for all your hard work. look forward to more updates..

Just text him.

I could be wrong, but I don’t think the mesh in the original part adds any rigidity. As far as I can tell, it’s cotton or a similar material. It certainly adds shear and tensile reinforcement. I think those that are focusing on the mesh as a component of rigidity that prevents collapse have not fully examined a failed boot in a while. They tend to tear from the shear stresses that come with start up and shut down. They tend to fail in same place and the resulting tear tends to look like rubber coated denim that has a hole in it with frayed and soft fabric at the edge of the tear.

Nicely done!

You might be right. Its been such a long time since I’ve run 50ROP that I don’t have much of a frame of reference.

Remove the overhead interior trim to find out what happened to the nut. If I recall correctly, it’s anchored into the steel tubing. It’s likely still there, just misaligned with the hole in the trim.

Fair enough. The F model has no grommet in that area as far as I know ( none shown in IPC). My governor line is fire sleeved so there’s not much of a gap anyway. Even so, prior to sleaving it, CHTs were well controlled( high200s to low 300s in cruise). It certainly is important to ensure proper airflow through the cowl both in volume and direction. However I’ve seen many planes with a lot of attention focused on things that don’t really do anything…Lord, deliver us from copious amounts of RTV. I think something else is going on that is either causing the top side flow to leak past the engine compartment or the bottom side is not evacuating air from the lower cowl for some reason.

Even if it were missing, that would not cause your CHT issue.

Are you sure the rear baffle seal was dressed forward so that it sealed against the cowl under pressure? It looks like it could easily be faced the wrong way. I learned early on in my ownership experience that if the rear seal is folded back rather than forward, cooling capacity is diminished a great deal.

Thanks,, that makes sense. However, does that not mean that the calculation is useful for calculating the initial Vy number by weight if you were so inclined. So if we use my initial calculation. Book Vy at max gross of 2740lbs =99kts Take off weight me with 4hrs of fuel = 2135lbs 2135/2740=.78 √.78 = .88 .88*99kts = 87 Calculated Vy at 2135lbs = 87kts And then compare book Vy at some higher altitude, (The book simply decreases the initial Vy number by 1 mph per 1000ft). We see the: Book Vy at 2740lbs @ 9000ft = 90kts Calculated Vy a 2135lbs @ 9000ft = .88 * 90 = 80kts or if we just subtract 1 mph per 1000 ft of altitude as the book does (9mph =7.82kts) we come up with 87kts -7.87kts =79kts So the results of calculating by sqrt of weight and subtracting 1mph per 1000ft differ by a rounding error.