Monday, March 31, 2008

Be nice to your engine - some tips

Runway 17, Alpine County (M45)

Reciprocating engines use petroleum oil to lubricate surfaces. A running engine's critical surfaces are kept apart by a very thin film of oil. A piston pushes on a rod which pushes on a crankshaft bearing surface (called a journal). This is where reciprocating movement is changed into rotational movement. The downward force by the fuel burn on the top of the piston is tremendous. It's 0.5-2 thousands of an inch of oil that keep metal-to-metal contact from occurring at the bearing surface when these forces occur. Also, protection of this surface under high load conditions requires that the oil is warm (usually around 180 degrees F.). Putting a high load on a cold engine immediately after starting is destructive because oil that was on the surface when the engine last ran has drained off, it is hard for the pump to move viscous cold oil to the bearing surface and when the oil flow reaches the surface its lubricating properties are poor until it warms up. Learn to position the throttle so that when the engine starts RPM is around 1000 or less.

On cold days with cold engines, prime the engine early, right after checking fuel quality. An engine will not start unless vaporized fuel is available to the cylinders. An engine will not start well or at all on atomized or liquid fuel. Trying to start an engine without vaporized fuel and flooding are the common causes of pilots grinding on the starter motor to get the engine to start. Grinding a starter motor for extended periods can deep cycle the battery. On a cold day with a cold engine, an early prime allows time for fuel vaporization. By doing this you will usually find that your engine starts up easily with very little load on the battery. Be sure to skip the priming item in your check list if you do an early prime. If you would rather to do it according to an approved check list, then prime, but wait a minute or so (with the master switch off!) before activating the starter motor. Large, high horsepower engines start noticeably easier when primed in this fashion. Bonus question: why wait until after checking fuel quality before doing an early prime?

Airplane batteries are not made for deep cycling. This means that if you severely draw an airplane battery down a few times, it's ready for the trash heap because it will never again hold a charge. (Cruising sailboats have deep-cycle batteries because they are drawn on for many hours between engine operation when the battery is recharged. Automotive batteries will fail after about 30 deep cycles whereas they will last for thousands of cycles if only used for starting, a 2-5% discharge. Marine batteries are designed to handle 80% discharges over and over.). If you find this topic electrifying, see http://www.windsun.com/Batteries/Battery_FAQ.htm.

If you have cowl flaps and it is a cold day, don't open the cowl flaps during start, taxi and run up. Most manufacturers state something to the effect: open cowl flaps as required. Watch your temperatures. Cowl flaps are required with high cylinder head and oil temperatures, not likely for a first start of the day and several minutes after on a 40 F. morning. With the cowl flaps closed, your engine oil will heat faster. Run ups should be done with the oil temperature needle in the green and this can take time with a cold start on a big engine especially on a cold day. When you cycle the prop you are making sure the governor and prop are functioning and at the same time applying warm oil to the prop hub cylinder. That oil isn't going to be very warm if you do the prop cycle with cold engine oil. (I won't get into the religion of prop cycling during run up)

Be kind to your engine and it will be kind to you (and your wallet).

Saturday, March 15, 2008

How to make good landings

Cotton Under Wing

Introduction

I tried to write about the entire landing process. I gave up - it's too much so let's start at the beginning and I will end at the end at some other time.

It is said that the good landing starts long before reaching the runway. For your information, I have re-discovered that this is true and I spend a good deal of my time as an instructor convincing others that this is true. A good landing starts with a mind set by the pilot long before the final leg. The good pilot pays attention to his perceptions and carefully executes measured responses to these perceptions. Landing an aircraft is very much a skill of executing a picture based on one's perceptions. Merriam-Webster defines art as a 'skill acquired by experience, study, or observation'. Another definition of art is the 'creation of beautiful or significant things'. I know a beautiful landing when I see one and I know it requires a skill acquired by experience and observation.

Paraphrasing those, on whose shoulders I rest, "landings are one possible outcome of a go-around"; if you happen to see a good landing evolving in your go-around attempt, take it and then glow in the cult karma of 'the wheel greasers'. The flip side of this coin is that if the landing is going to be something other than greased, then by all means, have a nice go-around. And by the way, kudos because your perceptions told you your art was bad, you weren't drawing the correct picture. This is the first step to being good at landing. The go-around model of landing is great advice: if it ain't working, go around, don't force a landing that was not meant to be. Some pilots have many more good landings than go-arounds. Why? What leads one pilot to grease the wheels on almost all landing attempts and the others have this experience at a low frequency even after years of flight? The answer is that those who fully understand the picture they are supposed to create using their brushes (pitch, roll, rudder, power, trim) become good landers.

The Pattern Before Final
After initial descents or climbs into the pattern, a good pilot maintains pattern altitude and an airspeed that is not too fast and not too slow, but just right. This will vary from aircraft to aircraft and with external conditions. When it is gusty, a pilot will want a slightly higher airspeed for better control of the aircraft. (I would mention some airspeeds for typical trainers, but I would rather not broach religious topics in this blog - see your clergy person at your local Faith Based Operation otherwise known as an FBO). As the good pilot closes in on the working end of the runway, s/he is tightening tolerances by catching lateral, altitude and airspeed errors earlier and earlier in order to minimize how much the aircraft position must be changed to correct an error.

The Final Approach
Recall that tolerances are being tightened by the pilot; there is less and less room for corrections as the pilot nears the runway. Here is the key: big corrections near the ground are at best the worst thing you can do and at worse dangerous. The good pilot is catching errors while they are almost imperceptible to the eye and corrects with control changes that are of the smallest required movement to make the appropriate correction. Whoa, that last sentence was vague - what does that mean? It means that sometimes little tiny corrections are needed to move the aircraft a few centimeters to stay on the two dimensional glide path, and sometimes big control movements are needed to move the aircraft a couple of centimeters to stay on the glide path, but in either case, the parameter in error is corrected by exactly the right amount and the magnitude of the correction is small. Do you see the common thread? In one case a slight puff or perhaps a slight reduction of cross wind velocity made the aircraft move off line and in the other case, it was perhaps a serious wind shear. In both cases, the correction was a few inches, not a few yards, if you will allow me to mix my metrics. A lot more control movement was required in one case, but in both cases it was just the right amount and it led to very little movement of the aircraft. The 'right amount'? The right amount is the amount of paint an artist uses when conveying her mental perception onto paper with a brush. The 'right amount' is the amount of control reactions (throttle, ailerons, pitch, rudder) the pilot uses to create a picture of the perfect landing. Picture, what picture? The picture is the view the pilot sees looking out the window. If you are having trouble with your landings, ask your instructor to do landings more often and relax, listen and watch the picture s/he draws in and out of the cockpit as the artist works her palette. As an instructor, I am frustrated that many pilots insist that they attempt all the landings during training when I know they don't see the picture. The best artists study the art of other artists to help them develop their skills and yes, the best artist try, try and try again. It takes a keen understanding of what exactly the art is and then repetition to improve one's skill to accomplish the art. If you don't have the picture, you will never get the art.

Why is Early Error Correction so Important on Final?
It is simple: last minute corrections destabilize your artistic effort. Bank and pitch changes used to correct large errors are dangerous when applied near the ground. This is because on short final your aircraft is slow and draggy and it requires large bank and pitch changes to correct errors. Massive attitude changes near the ground can cause all kinds of problems from stalls to planting a wing tip or nose wheel into the ground, etc. Understand the forces working against you long before reaching the runway and correct early when errors are minute. As you approach the runway, airspeed should be nailed to a perfection, the aim point doesn't move and you have the aircraft tracking the extended center line. Mess this up and it's a given that you will have either a messy landing, or a wonderful go-around opportunity - your choice.

Sunday, March 2, 2008

Some interesting URLs for All Pilots

Another cruddy day over San Francisco


AOPA
:

You may have to be an AOPA Member to see these, I am not sure. I find the following articles interesting and these and many more can be found here.

Your airplane:

To download a set of flashcards that you fill in to describe important facts about your airplane click here (1.7MB PDF). Fill in details such as emergency procedures, air speeds, fuel data, etc., and use the cards later for a mental refresh.
Runway Markings:
If you want a great way to learn and review runway markings, click here for a 700KB low resolution version or here for a 3.4MB high resolution version of the same file.
Accident reports:
All pilots should read the Nall Report on a regular basis to understand the common causes of accidents. If you click here you will get a list of accident reports by the year. Another interesting AOPA web page, known as featured accidents, in which accidents are highlighted and used to illustrate how pilots get into trouble. Featured accidents are updated every two weeks, so reference this page often. Pilots should read accident reports to understand what to do and what not to do when they encounter situations similar to those that led to these accidents. It's useful to second guess a pilot that has had an accident, but what would you do during an adrenaline rush if the same thing happened to you?