On the dismantling side of the project I have removed the fore and aft windows on both sides of the aircraft, stripped the old paint from the cockpit interior, removed the old radio and wiring harness and removed the old antenna and cable. On the put-it-back-together side I have repainted the cockpit interior, installed a new antenna with skin doubler, installed new antenna cable (RG-400) and routed it to the new radio, installed the radio box in the hole left by the old radio, wired it into the existing PM-1000II intercom and successfully accomplished the operational checks specified in the radio and intercom installation manuals. I have also moved the headset and mic jacks from the instrument panel to the underside of the aft shelf behind the outer edge of the left and right seats. The forward location of the jacks was probably acceptable when the aircraft had yolk controls but this plane has a dual stick conversion STC installed and the forward jack location could easily allow interference between the stick movement and the headset cords. While I was working in the cockpit I also took the time to move the fuel quantity gauge for the outer wing aux. tanks from its position aft of the main tank gauge on the little center console to a blank space on the instrument panel. In order to read the aux. fuel quantity with the gauge located in the center console (even with my right hip) I had to turn sideways in the seat. The switch for the gauge that selects either the left or right aux. tank quantity for viewing was located on the instrument panel. Now the gauge and selector switch are next to each other.

The notes on the project progress that I left for myself show that the items remaining to be accomplished include completing the radio box installation by adding a vertical support at the rear of the box per the installation manual, the final wiring of the mic and trim buttons on the sticks and adding the wiring supports, grommets and protective sheaths along the wiring runs as specified in AC43-13. That will just leave the installation of new windows.

Let’s see. That’s about a week’s work so it will probably take two months to complete, especially when you consider I’m currently 4 days into a 14-day airline trip. That day job is getting in the way again…

I won’t say what I found when I removed the old antenna other than to say that it hadn’t been installed using the best practices. In order to correct the workmanship and install the new antenna correctly I would have to install a doubler under the antenna. That would involve stripping the ugly yellow/tan paint away from the area below the antenna before doing the riveting. Stripping the paint in just a small area and then painting a new color wasn’t a good idea, so now I was looking at stripping the ugly old paint in the aft area of the cockpit and repainting the whole thing. Now I needed to remove the shoulder harness installation, the electric pitch trim motor and lines and the rear windows. This list is not getting shorter!

Last week I finally completed the stripping process. That cleared the way to rivet in a doubler for the new antenna and to install a flush patch in the place of an ugly scab patch that had been installed on the top of the fuselage. I finished that two days before I was to leave on my next trip, then spent the next day doing a final cleaning and masking in preparation for the new paint. I chose a medium gray acrylic enamel for the project. First I sprayed on a self-etching primer, then followed with two light and one medium color coat. The blue lines you see dangling in the cockpit are the loop of the elevator trim cable and the power lines for the electric trim motor which is now sitting in the bottom of the cockpit. They are masked off with blue painter’s tape.

The painting directions said to wait seven days for the paint to cure before adding additional coats. That happens to be just the amount of time that my airline trip is taking, so when I get back I’ll evaluate whether the job requires any additional painting. If the paint coverage still looks good, I’ll remove the masking reinstall the trim and shoulder harnesses. Then I’ll get some new window material, make some aluminum frames for the inside of the window, paint them and reinstall the windows with new frames. THEN I can get back to the antenna, cable and radio installation.

Remember, when you estimate the time it will take to complete a project on an airplane, make your best guess then double it and go to the next higher unit. A one-week project will probably take you two months, if you’re lucky.

Ben Visser, Staff Research Engineer, Shell Oil:

“Preheating your engine makes a world of difference. It heats the oil so the oil is thin enough to flow through the engine and properly lubricate all of the critical wear surfaces. Preheating also heats the metal parts in the engine. That’s important because aluminum crankcases have a higher coefficient of thermal expansion than iron crankshafts. This means as your engine cools down, the clearance is reduced. And as a result, you may not have sufficient oil film thickness for proper hydrodynamic lubrication at very cold temperatures. In other words, the wear rate is going up. If you’re using [an electric] heater, make sure it’s a system that heats the whole engine, not just the oil.”

I made a small pre-heater for my plane that forces hot air into the engine compartment from below, allowing the warm air to heat the oil sump and then to flow up around the cylinders and out the front of the engine, using the reverse of the route used by the cooling airflow during flight. 

I bought all of the materials for my pre-heater from one of the local home improvement centers like Home Depot. The heat source is a small portable ceramic heater. The sticker says it is a Ceramic Safe-T-Furnace, Model HC-441W (made in China, of course). It has a built-in fan and a plunger-type safety switch on the bottom that will shut the unit off if it tips over. There are both fan speed and heat controls on the front, though I just set both of them to their maximum settings and leave them there. I also have a piece of tape on the bottom of the unit holding the safety switch depressed. As you can see in the photo, the unit is tipped slightly forward and the tape keeps the unit from shutting off.

I used a square to round flange adapter similar to this larger version and tapped it to the front of the ceramic heater to use as a transition to the round ducting, then attached a length of dryer duct to the adapter to direct the heat upward. The duct is a very flexible expandable metallic tubing that is easily molded to any shape that you might need.

I used the pre-heater with bare tubing for a little while, then decided that the unit was transferring too much of it’s heat through the thin-walled ducting, so I bought some self-adhesive insulation and wrapped that around the duct leaving the last 6″ or so uncovered so that it could be squeezed into an elongated oval in order to fit up into the cowl. The adhesive on the insulation wasn’t staying attached to the uneven surface of the duct, so I wrapped the whole duct with aluminum tape that is used by HVAC installers.

I also use 2-3 layers of blankets and carpet remnants over the engine compartment to help reduce heat loss. When I intend to go flying, I plug in the unit, make sure that the fan is operating and then go about my preflight duties. If it’s really cold, I will often make a trip to the local coffee shop for a few minutes and give the unit about an hour to work it’s magic. By the time I return there is a noticeable flow of hot air coming out of the front of the engine and the blankets/carpet over the top of the engine compartment are warm to the touch. The engine always turns over easily during start and the oil pressure indicates quickly.

I don’t know how much the pre-heater cost to make. I do know that I bought more material than I needed for the project because smaller quantities were not available. Two people could probably build units and split the costs. I did notice the other day that you can buy the flexible ducting with insulation already attached. Bigger heaters will, of course, pump out a larger volume of hot air and will do the heating job a bit quicker, but they would also need a larger diameter duct to move the air.

I’m sure other people have made more elegant and more professional-looking pre-heaters, but this one works for me and it seems like it will last for quite some time. It looks like the temperatures are starting to trend higher now, so maybe by the end of the month I’ll be able to put it away for the summer.

Update:I first posted this article on the evening of March 8th after a beautiful, clear day with temperatures in the low 50s (F). It is now 8 am on the morning of March 9th and I am looking at a thermometer indicating a temperature of 22° F with 5″ of new snow on the ground. Maybe I won’t put the heater away this month…

Traffic was backed up a little as we were leaving Tokyo the other day which meant we had to to wait in line on the parallel for our turn to take off. We happened to stop just abeam a parking apron where a maintenance crew was readying a 747 for tow. They were using one of the big tugs that can lift the nosewheel off the ground and capture it in a cradle. This makes it very easy to maneuver the aircraft from one position to another and gives a very smooth ride if the plane is full of passengers. The tug also has auxilliary electrical power capability. You can see the yellow power cord coming from the tug, looping around the steering cylinders at the rear of the nosewheel strut and connecting to the plane. It’s not obvious what the other line is that is coming out of the nosewheel well, but it is probably the cloth streamer attached to the end of the nosewheel pin. The pin is inserted into a hole in the nosewheel retraction mechanism to prevent the gear from retracting. I have seen these tugs moving 747s around at what seemed like 30 knots. It was probably not that fast, but it was definitely faster than a brisk walk. For those of you who may be curious, the ANA on the side of the tug stands for All Nippon Airways. If you have really good eyes, you can see the letters NCA on the underside of the aircraft nose. That’s a Nippon Cargo Airlines 747-400 freighter, not the private plane of the National Cheerleaders Association. (Amazing the things you find with a Google search.)

I watched the maintenance crew for a couple of minutes before we moved up in line for takeoff. It reminded me of a unique tow method I came across while at the Reno Air Races last year. Tulsa Towbots had a booth set up in the pit area and was offering their Towbots for sale. I saw several Towbots in use in the race pit area and then later, at the end of the event, in the National Aviation Heritage Invitational area where they were moving some of the larger aircraft involved in that competition. The unit looks and works very much like a miniature of the ANA tug. It is radio controlled using a handheld control unit. You run the unit right up to the aircraft wheel, maneuver under it, and roll the wheel up into the unit where it is clamped it in a little dolly. The dolly is able to swivel 360 degrees on it’s own axis. That means that the maneuvering of the aircraft can be done without the aircraft nosewheel (or tailwheel) having to swivel on it’s own. There are several models available including a small aircraft version, a BomberBot capable of moving large warbirds, a model for helicopters and a version for use with aircraft that have wheelpants installed. Their web site shows the various models and has videos of their operation. It’s a great piece of equipment – and a really good idea for a Christmas present!

Maintenance Discrepancies

What do you do when that happens to you? If you found something mechanically wrong with the airplane that you were about to fly, what would be your next course of action? (Let’s make the assumption that you’re making a Part 91 flight rather than flying a charter or scheduled air carrier flight.)

You would probably ask yourself a few questions. For instance -  Is this item required to be operating for my flight? The answer to this question would depend on what kind of flight you are about to make – day or night, VFR or IFR and whether the item is on the list of required equipment for that type of flight, as listed in CFR 91.205. It would also depend on whether the item is listed in the airplane manufacturer’s list of required equipment or specified as required by any installed Supplemental Type Certificate (STC) modification or required by an Airworthiness Directive (AD). Lastly,  it would depend on whether or not the airplane you were about to fly has an approved MEL, or Minimum Equipment List that includes the item.

CFR 91.213 says that you cannot takeoff unless you have taken care of the inoperative item in one way or another.

What’s an MEL?

Airplanes are getting more and more complex with every iteration. Large transport category planes are filled with items that, if they become inoperative, have no real bearing on the flying ability of the plane. Let’s say, for example that an engine-driven generator failed for some reason. Without some sort of dispensation, if the generator could not be fixed, the plane would be grounded. Enter the MEL. The airplane manufacturer, operator and the FAA get together and look at each item in/on the airplane and decide whether or not it is actually necessary to have that specific item working to make a safe flight. If this happens to be a four-engine aircraft and the other three engine-driven generators can easily provide enough electrical power to operate the aircraft equipment, the MEL might say that although four generators are installed, only three have to be operational. Then the MEL would go on to give the specifics for the situation. It would list any flight crew procedures that would be required, such as ensuring after engine start that the remaining generators are all working normally. It would also list the specific procedures that the maintenance personnel would be required to perform to safely disable the generator and where to place placards in the cockpit to alert the crew to the discrepancy. It would also specify how long the generator would be allowed to be inoperative before it would have to be repaired or replaced, usually in a specific number of days or flights.

Any aircraft can be operated using an MEL system, though the complexity of setting up the maintenance program for a typical single-engine general aviation airplane generally does not warrant the effort. The MEL program is described in Advisory Circular AC-91-67, dated June 28, 1971.  The process involves visiting your local FAA FSDO (Flight Standards District Office) and obtaining a copy of the Master Minimum Equipment List (MMEL) that has been generated for your type of aircraft. You and your maintenance adviser/mechanic would then compare that MMEL with the equipment in your specific aircraft and make appropriate additions or subtractions and develop procedures specific to your aircraft. This MEL modified for your aircraft would then be submitted to the FSDO for approval. I would imagine it would take several iterations before an MEL was finally approved but once it was, you would be given a letter of authorization to operate your aircraft (specified by serial number and registration) using the MEL process.

What if it isn’t listed in the MEL?

Ouch! You just went through that whole process and have an approved MEL for your plane and now something not listed in the MEL has broken. Short answer: You’re grounded until you can fix it, whether you need it or not. If the item is not listed in the MEL with an associated maintenance procedure, then the item has to be fixed before you can make your flight.

And that’s why most light planes don’t have an MEL program. Without an MEL, if something breaks, you first determine if it’s required by the regulations, STCs or ADs. Then you, as the PIC determine if the proposed flight can be safely completed without the equipment. If you can, then your mechanic can either remove it or safely disable it, placard it inoperative, put the appropriate words in the maintenance records and you’re good to go. You can then make the flight with the item inoperative, with the requirement specified in CFR 91.405 that the item be repaired or permanently removed at the next required inspection (annual or 100-hour).

Did we get to the beach?

Yes, we did, but not on that airplane. The mechanic had found a 3/4″ crack in the aircraft skin where one of the bathroom exhaust vents exits the side of the fuselage. A long discussion followed which was hampered by language and the need for decisions to be made in the U.S. and then relayed to Japan. Not a very efficient system in this situation. Luckily this particular aircraft was equipped with a satellite phone system. The Captain was able to talk directly with the flight dispatcher and maintenance control. The end result was that the aircraft was grounded and we waited for another flight to arrive so that we could take their plane. We got to have our umbrella drinks on the beach, but it was a few hours later than we had planned.

Related Links:

Advisory Circular 91-67, Minimum Equipment Operations for General Aviation Operations under FAR Part 91.

CFR 43-11, Records for Inspections Conducted Under Part 91.

CFR 91-205, Instrument and Equipment Requirements.

CFR 91-213, Inoperative Instruments and Equipment.

CFR 91-405, Maintenance Required.