Sunday, November 28, 2010

Oil Change

Yesterday was the day to change N631S's engine oil. It's a long weekend and the time was available. The oil had 46 hours on it - it was about "used up." And finally, cold weather is upon us. The oil that had been in service for the last three months is Aeroshell 100W, which has an SAE 50 viscosity rating. For the winter months I like to switch to less viscous Aeroshell 80W, an SAE 40 oil.

Of course, changing the oil is one of the items of Preventive Maintenance authorized for accomplishment by the holder of a Private Pilot's certificate under 14 CFR 43 Appendix A Section (c).

To change the oil in a Cessna 182 the following items are essential:

  • 10 quarts of oil;
  • An oil filter;
  • An oil analysis kit;
  • Safety wire (the 0.032" flavor);
  • Safety wire pliers;
  • A couple of small nylon cable ties ("Ty-raps");
  • A torque wrench with a 1" socket;
  • A 5 gallon pail;
  • The usual array of basic tools;
  • A helper (to wrangle the lower cowl).
My first step on arriving at N631S's hangar is to remove the top cowling and hook up the Tanis engine pre-heater. The oil has to be warm to drain properly and there are two ways to make that happen - go fly the airplane, or apply pre-heat to the engine. It's easiest for me to use the electric pre-heat system for an hour, since pattern operations are not permitted at KVKX ("National Security" and all that).

To drain the oil on a 182 you have to remove the lower cowl. To do that, you first have to separate the halves of the landing light electrical connector. It lives just inside the access door for the oil dip-stick and is normally secured with small nylon Ty-raps (to prevent the connector from separating due to vibration). Cut the Ty-raps and split the connector.

Next, disconnect the cowl flaps from their operating cables. A 3/8" wrench and 3/8" socket on a small ratchet work out nicely. The nuts are elastic stop nuts with nylon inserts, with a flat washer under each. For each cowl flap, remove the nut and washer, pull the bolt out of the clevis, let the cowl flap drop and put the bolt back in the clevis. Secure the bolts with the washers and nuts so that the hardware bits can't go adrift and get lost.

The third item is up there in the darkness beyond the cowl flap. The air inlet duct from the air filter is secured to the carburetor inlet air box on each side by a 1/4-turn fastener. If you are fortunate they will be "wing-nut" sorts of an animals and you can reach way up there and separate them manually. If you are not so fortunate you may have to engage them with an appropriate screwdriver, which is more difficult and requires more colorful language.

Once all three connections are disconnected you can unfasten the 1/4-turn Cleco fasteners that secure the lower cowl in place (taking care not to forget the two that are way down at the bottom just to the left and right of the nose gear strut) and carefully lower the cowl clear of the exhaust pipe and carry it away. (This is where your helper earns his keep.)

Now you'll be wanting to get the oil started draining. It's really good if one of these "quick drain" fittings (at left) is installed. You can push and turn the knurled collar and the fitting will lock in the open position to allow the oil to drain. On N631S, a piece of 1" Tygon tubing about two feet long fits nicely over the quick drain and allows the oil to flow into the pail in a neat and orderly way. Once the oil is draining you can turn your attention to the filter.

The oil filter is located so as to maximize awkwardness. Access to the filter is obstructed by various components and parts of the engine mount. To further complicate matters, the filter is full of oil that will want to get out and get all over everything as soon as you try to remove it. Everyone has their own set of home-brewed procedures to minimize the mess - here's what I do. First, I reach in with a pair of cutting pliers and cut the safety wire. Then, I use a 1/2" drive ratchet with a 1" socket to loosen the filter until I can just turn it by hand. I then slide a one gallon zip lock plastic bag up over the body of the filter.

Then, the special tool shown at left (an old oil bottle with one side cut out of it) gets slid under the bag and filter to (I hope) collect oil that may escape.

I unscrew the filter as quickly as possible, keeping a roll of paper towel handy.

Once the filter has been detached and extracted and the area has been cleaned up, untwist and remove any left-over safety wire that may still be hanging from the filter adapter. Then, take a good look at the filter adapter. There is an Airworthiness Directive, AD 96-12-22, that applies to Cessna 182 aircraft. It requires inspection of the oil filter adapter at every oil change and in particular focuses on the integrity of the torque putty applied to the joint at the base of the adapter. (If the putty is broken it indicates that the filter adapter is not secure.) This is one of the few inspections that can be accomplished by a Private Pilot, and it has to be logged in the airplane's maintenance records.

The oil has been draining for a few minutes by this time so it's a good opportunity to capture a small sample of the used oil to send off for spectrometric analysis. I use the kits provided by Aviation Laboratories of Houston, Texas. They provide very nice on-line reports of their analytical results.

As the oil continues to drain you can thread the new filter into place, having coated its rubber gasket with Dow-Corning DC-4 silicone grease (or, if you are fresh out of DC-4, a film of clean engine oil). Use your calibrated torque wrench (as shown above) to tighten the filter to a torque of 16-18 ft. lbs.

Cut a longish piece of safety wire (a couple of feet at least) and thread it through the drilled "ear" on the filter adapter. Pull the wire through until you have two strands of equal length. Mark a spot on the double strand corresponding to the distance to one of the holes on the filter - pick one that, if restrained, will prevent the filter from "unscrewing." Add about 20% more length to account for the fact that when you twist the wire it will shorten up, and clamp the safety wire pliers onto the two strands at that point. Use the pliers' twisting mechanism to twist the paired wire, aiming for about 6 to 8 turns per inch.

When the length of the twisted wire is about right to reach the tie-off point on the filter, thread an end through that hole and then use the pliers to twist the free ends together thus securing the filter. Cut off the excess wire, leaving about a 1/2" "pig-tail" and use pliers to turn the pig-tail under, so that the next person to stick their hand near there doesn't get "bitten."
Now the filter is securely installed, and the oil is probably about done draining from the crankcase. Close the quick-drain fitting and begin pouring quarts of fresh oil into the engine. The crankcase capacity of the O-470 engine in the 182 is 12 quarts but I've learned that the engine will blow off two quarts very quickly and will settle down at the 10 quart level. So I put in 10 quarts to begin with.

With the oil in the engine, pull the airplane out of the hangar and start it up. Watch the oil pressure closely, and if the gage doesn't respond in a few seconds, shut down and find out why not. Don't run the engine too long, as it's un-cowled and therefore isn't being cooled properly. After a couple of minutes shut down and inspect the engine for any evidence of leaks.

If everything looks tight and dry you can re-cowl the airplane (usually the hardest part of the entire job). You'll need your helper again to get the lower cowl in place. Remember to re-secure the two fasteners for the air-box duct, the two cowl flap clevises and the landing light connector - which will need a couple of new Ty-raps.

And that's it! All that's left is to make the appropriate entry in the engine's maintenance log, send off the oil sample to the lab, and cut open the filter to inspect the media for stray metal (which process will be the subject of a future post.)

Thursday, November 25, 2010

An Existential Question

Photo: Paul King Mansfield
A very savvy young lady named Toria flies and works in the aviation industry in Maryland, and maintains an excellent blog called Toriaflies. Recently thereon, she posed what is (to me, at least) an existential question: "Why do you fly?" She offered some answers she'd gotten from friends, as well as her own, and solicited responses from her readers.

The question got me to thinking about, first, why do I fly? And second, why do all of us fly? At first, specious answers suggested themselves:

  • "It's fun!"
  • "Flying is so convenient."
  • "Because I can!"

But none of the easy answers really captured the motivation that leads me to engage in a costly activity with (let's face it) heightened risk, on a regular basis. In the end, this is the response I gave to Toria's question:

Why do I fly?

I fly because in flying there is no pretense, no prevarication, no dishonesty. The airplane doesn't know your family name or your pedigree. It can't read your resumé or check your references. It cares not about the color of your skin, or your gender, or where, if anywhere, you bow before your god.

The airplane only cares that your hand and your mind and your heart can become one with it when, together, you have to deal with the fierce crosswind, or the frontal weather, or the icy threats of winter.

The airplane looks back at you and says, "Do or do not. There is no 'try'." But when you give the airplane what it needs from you, it returns a satisfaction that is rare in our world. And that is a priceless gift.

But that's just me. Other pilots certainly respond most powerfully to other satisfactions. Some relish the freedom of flying a J-3 Cub from a rural grass strip and cruising, low and slow, over the countryside. Others may crave the adrenalin rush that comes with taking a fully aerobatic Yak-52 to the edge of its performance envelope for an air show crowd. The warbird owner may sacrifice many things for the feeling that when he keeps his 65 year old T-6 flying he is in touch with, and part of, the amazing tradition of aviation in America.

I'm pretty certain that there are almost as many reasons to fly as there are aviators. And that's a wonderful thing because it preserves the variety and vitality of aviation.

So, my flying friends, think it over for a few minutes. Of all of the reasons to fly, all of the rewards to be had, which one speaks most clearly to you? And when you have it figured out, go on over to Toria's blog and leave your answer to her question.

Wednesday, November 24, 2010

'Blow, Blow, Thou Winter Wind'

-- As You Like It (II, vii)
The cold front marches offshore and the skies are a pellucid blue; the usual aftermath of strong winds from the northwest dominates the weather story in the northeast. The Terminal Area Forecast (TAF) for KBDR is predicting 33018G29 for winds this afternoon. That's a steady wind of 18 knots from 330 degrees with gusts to 29 knots. The favored runway will be 29 so for departure N631S and I may see a right crosswind component of about 12 knots with potential gusts to 20 knots. That will require good crosswind takeoff technique.

I could cheat a bit by lining up toward the left side of the 150-foot-wide runway and angling my initial takeoff roll into the wind to cut down the crosswind angle. I'll see what the actual conditions are when the time comes.

The image clip at left is from the winds aloft page at Aviationweather.gov. The forecast shown is for 20Z at the 725mb level (about 9,000 feet - close to my initial altitude of 8,000 feet). I've approximated my planned route of flight in red; you can see that the headwind components will be significant. I expect I'll have a long time (FlightAware.com says 2:35) to enjoy this flight.

But the skies are clear and I'm going home for the holiday weekend. Life is good! To all who visit here, safe travels and a fine Thanksgiving.

Saturday, November 13, 2010

It Doesn't Get Any Better Than...


The city of Baltimore, looking west from 6,000 feet above the outer harbor. The dark area on the left is the Inner Harbor. Usually N631S and I are routed directly above the Inner Harbor on the way down from Lancaster (LRP) to Baltimore (BAL) but last night we were vectored out to the east for KBWI traffic.

The FlightAware track at left shows the deviation, which ended up with "direct Nottingham" then the visual approach to runway 6 at KVKX.

The weather gods delivered as promised for this flight. It was a perfectly clear, moonlit night with temperatures aloft well above freezing and a tailwind! Ground speed for most of the trip down from Bridgeport was around 145 knots and the time en-route runway-to-runway was 2 hours + 7 minutes. What a superb flight!

And, a shout-out to Sarah. I guess I wasn't routed through your sector this trip. Maybe next time!

Wednesday, November 10, 2010

What's Not to Like?

Looking ahead to Friday, it seems to be shaping up as a lovely evening to fly from KBDR in Bridgeport to KVKX in the DC area. All of the weather indicators are good.

The synoptic picture, courtesy of NCEP, shows high pressure dominating the eastern seaboard as of 00Z Saturday (i.e., 7:00 PM EST). The front running from the Great Lakes southwest to Texas won't be a factor.

The trough that dragged cold arctic air down here to give us a chill the last few days has moved off to the east and the freezing level will be high. The chart at left from ADDS shows the isotherms at the 725mb level (about 9,000 feet). My route will be well south of the 0 degree curve, so even if I can find a cloud it will just be wet. And both the NAM and GFS Model Output Statistics are predicting ceilings above 12,000 feet and excellent visibility across the route.

And finally, I note with some amazement that N631S and I may even get a tailwind! The wind speed chart at left, also from the ADDS site, indicates a bit of a push (maybe 10 or 15 knots) will be on offer for the southbound legs.

This is about as nice a weather picture as one could hope for in mid-November. If the forecasts verify, I'm expecting a beautiful evening flight.

Friday, November 5, 2010

It's an AmTrak Day

It's better to be on the ground wishing you were in the air, than the other way around. Or so I've been told.

This is the sky over Bridgeport, just a couple of miles from KBDR. That's about a 2,500 foot ceiling, and it's pretty representative of the whole northeast. The area forecast predicts tops at 8,000 to 10,000. Freezing levels are at 1,000 to 4,000 feet and that more or less tells the tale. Widespread icing conditions are not something either N631S or I can deal with so it's the train for me this weekend.

Of course, the forecast for Monday morning, when I will need to return to Connecticut, calls for fine, clear weather.