Friday, September 25, 2009

Aerial Crop Dusting

Every once in a while from the ground or up in the air, I see a crop duster at work. It is pretty amazing to watch. Then lately, I have been hearing how crop dusting or agriculture aerial application industry is doing pretty well and has advanced technically as well. It sounds like for the right person, it could be a good aviation career as an agricultural pilot.

Recent articles

Recently, there has been crop dusting articles in the Wall Street Journal and Associated Press. The Associated Press crop dusting article talks about the industry, and how it has increased recently. Some new sprays have come out for diseases that happen when crops are mature, these are hard to apply from the ground without destroying part of the valuable crop. Perfect for aerial application. In the Wall Street Journal crop dusting article, it also talks about how crop dusting is on the rise and is one of the few jobs a pilot can make decent money. But it really cautions that crop dusting is not for every pilot. This two articles sparked me to find an old AOPA Pilot magazine crop dusting article that I remembered from June 2007. It talks about how the industry has changed quite a bit to using GPS significantly for tracking and accurate spraying as well as using Air Tractor turbine driven turboprop planes or turbine converted older planes. If you can find your old AOPA magazine, I remember some good pictures to go along with the on-line article.


Pictures and articles don't do cropdusting justice, so I thought I would look on YouTube. Yep, there are some good videos there.

More Good Crop Dusting Information

Digging around a little more, I found an article on crop dusting and a little on becoming an ag pilot.

Then I found the most crop dusting information on an association for aerial crop dusting: National Agricultural Aviation Association (NAAA). On the NAAA web site there are multiple articles on becoming an ag pilot and getting a crop dusting job as well as links to FAA publications on crop dusting and other links as well as a convention coming up for crop dusting. Lots of good stuff on the NAAA site.

I also found this crop duster / agricultural pilot information on an aviation career website.


It is an amazing industry and amazing to watch the pilots doing their job.


Sunday, September 13, 2009

Airplane Mixture Leaning

Airplanes have manual leaning adjustments of the mixture for the engine. Every pilot knows about this engine management theory and might briefly discuss it during the private pilot training. But I was talking with my pilot friend the other day, and we both recalled that our introduction to this in our training was not very detailed. It is important to know how to use that red mixture knob during taxi, climb, cruise during a cross country trip, and approach to land.

Things do get a bit confusing since this subject is often debated.

The Controls and Instruments

Here are the engine controls in my plane: Carburator Heat, Throttle, Propeller Control, and Mixture.

C182 engine controlsHere is the standard C182 Instument cluster containing Cylinder Head Temperature (CHT), Oil Temperature, and Oil Pressure.

C182 engine instruments

Here is a picture of an Exhaust Gas Temperature (EGT) gauge that is sometimes found. This type only shows the temperature at one point instead of separately for each cylinder. The absolute temperatures are not shown since this is not as important as the number of degrees less than the peak EGT temperature. The yellow needle can be adjusted to line up with the peak that is found during leaning checks.

Single Point EGT gaugeHere is a multipoint engine analyzer which shows EGT and CHT for each cylinder. This is very good since different cylinders will be slightly different temperatures during normal operation. That way all cylinders are checked to be appropriate mixtures. Also if a cylinder starts having problems, it will show up here as one cylinder having a larger EGT or CHT difference.
In my C182, I pull partial carb heat while cruising so that my carb temperature is 10 degrees C. This makes the EGT differences between cylinders smaller and the engine operates a little better. Fuel injected engines will have even tighter EGT differences due to very even fuel distribution and this is part of why they operate a little more efficiently. If you don't have the carb temperature gauge, do not use partial carb heat; only full carb heat on or off.
C182 carb temp

Why Lean?

Leaning can be important for a number of reasons. It can give you better power and speed at altitude. You need to lean in order to plan your fuel more accurately for long cross country trips; you don't want to run out of fuel, and the performance charts count on you leaning. If you own your own plane, it saves you gas and money.

Operating to rich can lead to fouled spark plugs and then a bad mag check during runup; operating too lean (but not Lean of Peak) can lead to engine problems or reducing the lifetime of an engine.

Running Lean of Peak EGT is a hot point of debate, but it does not work very well in carburated engines like the older C182 so I will not talk about it much here.

How to lean is a choice you have to make. There is a lot to learn as well, and I am still learning/exploring. If you own the plane that is especially important. If you rent, you should probably use the owner/instructors recommendation.

Web Articles

I have been looking over the web extensively and trying to find articles that both describe how to run the mixture and the physics behind it. The best articles I think I have found are John Deakin's old Avweb Pelican's Perch articles. They talk a lot about engine operation and base it on physics. Much of it sounds like it follows what is taught at Advanced Pilot Seminars for engine management. He talks a lot about Lean of Peak, but I am trying to grab the information just on Rich of Peak.

John Deakin's articles:

There is a lot of detail there especially for the engineering minded person.

For pictures of what do do with a single point EGT, this Rod Machado article about leaning is pretty good.

Mike Bush's Savvy Aviator article list on Avweb is excellent for engine management and general airplane maintenance. There are a number of articles there; they basically follow the same principles as John Deakin's articles.

There appears to be quite of maintenance information the Sacramento Sky Ranch knowledge base web site.

I will try to summarize what I have read. See the full web site descriptions for more details.

Leaning for Taxi

Most people follow the recommendation to lean aggressively while taxiing. The idle mixture is set for starting an engine which is much too rich for taxiing. Prolonged taxi with full rich mixture will foul the spark plugs over time.

Mixture for Takeoff

Mixture should be full rich for all but high altitude takeoffs. Throttle should also be pushed full forward for most of the climb since that enables an extra richening feature in many carburators which is important for full power operation. Talk with an instructor for leaning at high altitude; you want to find the climb mixture, but on the ground before takeoff.

Mixture for Climb

When climbing, maintain the EGT that appears at Sea level when full rich or something around 250-300 rich of peak or richer for all cylinders. Most non-turbocharged engines have a peak EGT around 1525-1550, so this will probably be around 1275. Those are some typical numbers; you have to determine them for your engine and EGT probe location.

Leaning for Rich of Peak Operation

During cruise, the EGT setting is found as follows. Lean the mixture 1/2 turn counter clockwise, wait 3-5 seconds, and watch the EGT gauge. It will start going higher. Repeat until you see it go lower. The top temperature is the peak EGT. If you want to be 100 degrees Rich of Peak (ROP), then you want to enrichen the mixture back to the peak, then 1/2 turn clock wise rich, wait and repeat, until the temperature reduces by 100 degrees from the peak temperature.

If you have single point EGT, the above is close to what you want to do. It will only be checking one cylinder, but hopefully the probe is on the leanest cylinder by design. If that is the case, all cylinders will be 100 ROP or richer.

You might want different amounts of ROP depending on the percentage horsepower that your power setting is currently at. A particular Manifold Pressure and RPM setting will yield a particular horsepower that is specified in the POH. Be careful that your RPM gauge is displaying the correct RPM; many are out of adjustment and indicate lower than real. Check it with an optical RPM gauge. If it is wrong, you could be developing more HP than you think and be at the wrong ROP setting.

If you have a multipoint engine analyzer such as one by JPI or Electronic Instuments, there are usually automated ways to do this procedure. You want to do it so that all cylinders are the desired ROP setting or richer.

Lean of Peak (LOP) would be done similar, but all cylinders would be leaner than the peak and the richest cylinder would be leaner than the LOP setting. This is difficult in my carburated C182 engine due to uneven fuel/air distribution from the carburated system, and it is a very debated topic so I will not discuss it now.

The Red Box

Many places either talk directly about a red box or at least the need of not operating too lean while operating at high power settings or not being too lean when Rich of Peak. John Deakin refers to this Red Box description in his Pelican Perch article on Where Should I Run My Engine (Part 3-cruise):
  • At high power at Sea Level, operate full rich and full throttle for extra enrichening. This should place you at 250-300 Rich of Peak (ROP). Anything leaner is bad.
  • At about 80% horsepower, 200ºF ROP to 60ºF LOP is bad.
  • At about 75% horsepower 180ºF ROP to 40ºF LOP is bad.
  • At about 70% horsepower 125ºF ROP to 25ºF LOP is bad.
  • At about 65% horsepower or so, 100ºF ROP to Peak is bad.
  • At and below about 60% horsepower, there is no red box. Put the mixture wherever you want it.
So you would want to make the EGT Rich of Peak setting to be richer than the red box described above for the different power settings.

As the red box is described by John Deakin, it also means that 60% horsepower is a good place to be since any mixture is good. I have heard it is still best to make sure you preferrably don't end up with some cylinders LOP and some ROP. Aim for all cylinders to be all ROP or all LOP.

These cruise mixture settings will end up with richer EGT settings than what is specified in most POHs unless you are 60% hp or lower where any mixture is ok. If you believe John Deakin, Mike Bush, and Advanced Pilot Seminars, this is the way to go. I think it is the way I will aim to put my mixture. If your mixture is richer than the POH specified setting, realize you will burn fuel at a higher GPH rate.

Cylinder Head Temperature (CHT)

Through all these different mixtures, you should try to maintain a CHT lower than what the factory indicates. This will lengthen how long the engine will last and is easily attainable if the baffling and seals around the engine are in decent shape and control the air flow past the cylinder cooling fins appropriately. I try to keep my CHT under 390 degrees and preferrably much cooler. But John Deakin also advises in Pelican Perch to not adjust mixture for this top CHT temperature; adjust mixture with the red box in mind and then make sure it stays below a CHT threshold.

Burned Exhaust Valves

I am searching for articles on burnt exhaust valves as well and have found these interesting articles:

Once again, it is your choice on how to operate your plane. I am still exploring and learning. Talk with your mechanic, instructor, and others and form your own opinion. There are lots of opinions on this, and they seem to be in flux these days.

Any comments on my interpretations that do not involve Lean of Peak?


Saturday, September 5, 2009

Tailwheel Transition

Getting a tailwheel endorsement is a lot of fun. I just finished getting mine in a Citabria. See my earlier post about the Citabria for some pictures of the plane. I always like to keep learning, and I had heard that learning tailwheel will also help your non-tailwheel flying skills. It is also fun and will let me be able to fly a wider range of planes. I dream of flying in a super cub with bush tires some day.

So where to start... First, I picked up a book to hear more of the details, then I took a few initial lessons that combined tailwheel and aerobatics, then recently I focused on finishing up my tailwheel endorsement in a Citabria at Air West Flight Center. They have quite a few instructors that specialize in tailwheel and aerobatics, and I found one I liked there.

So here are my thoughts on the experience just after finishing....

Negative Stability

One of the biggest items to keep in mind is that the tailwheel is negatively stable when on the ground. When trying to slow down, the tailwheel plane wants to flip around since the center of gravity is behind the main wheels; this is especially true if landing incorrectly in a slight crab. If the plane flips all the way around, it is called a ground loop and is very bad. In tricycle gear, the situation is the opposite. In a slight crab while landing a tricycle gear plane, it will tend to correct itself and swerve a little back to the main direction of the momentum. So a tricycle gear pilot needs to be careful of this difference. This same tailwheel negative stability can happen during times other than landing as well. I think I might try to draw some pictures of the forces involved and put this in a separate post. The important thing is do the corrections quickly when they are still needed to be small.

The other item that makes the controls a little different for a tailwheel is the distance between the main wheels and the wheel for steering. The steerable nosewheel is much closer to the main wheels than the steerable tailwheel. The steering mechanism is also more like casters in a tailwheel; the wheel extends out horizontally from where the actual pivot center point is. These effects make the response time to steering input different and delayed. You have to be careful too much change in steering too late does not happen.

Taxi Operations

Forces during taxiing are different and stiffer in general in a tailwheel. If windy, it is harder to turn while facing wind, easier when faced away from wind. The plane will also tend to weathervane and push the tail where the wind is going. Taxi slow.

If you turn sharp, the tailwheel will pop out of the control of the steerable tailwheel rudder pedals. Then it is controlled by the brakes and wind over the rudder itself. Go straight again to have it pop back into standard steerable tailwheel control.

Remember typical wind control while taxiing. Climb into, dive away. But watch out for pushing the stick forward much if using much power; this reduces effectiveness of the tailwheel and can push the nose over if power is used at all. The Compleat Taildragger Pilot book refers to a different taxiing method, but I believe this is for non-steerable tailwheels.


Now for the first challenging part. Push full throttle, but keep stick buried backward initially so the steerable tailwheel is solidly on the ground. Then lift the tail at a certain speed by pushing forward on the stick until the attitude out the front window is correct. I was doing this around 40mph in the Citabria. You can get a little better feel of what is the level attitude when you get up in the air and cruising level; look where the horizon is on the windshield then. Back to our takeoff sequence. We are zooming along at 40mph+ and the tail up. If the attitude is right, the plane will fly off the ground gradually just like tricycle gear. If you hit 60mph+ and it is not, then pull the stick back slightly to let it fly off slowly.

Remember to not forget to lift the tail on takeoff. And lift it fairly quickly on a touch and go, especially if you did not slow down too much. If you do start taking off before lifting the tail, you are flying at a very low speed, so stay in ground effect until good speed is attained.

All that sounds relatively easy, but it does happen fast, and you have to be very good on the rudders through it all. That is what all of us tricycle gear pilots need to get better at. The left turning tendencies are changing constantly, so you have to compensate differently all the time. Be particularly attentive when you raise the tail. If you raise it faster, the turning tendency will change more significantly, and you will need to be more attentive. So raising the tail at a medium speed is easier. Once the tail is in the air, you are then susceptable to crosswind pushing the tail and any gusty winds; so continue to be attentive on the rudders.

Jabbing on the rudder pedals works well; be careful with sustained pushes. The effect of pressing the rudder pedal is a bit delayed and can easily be more than necessary, so a light jab works well.

Another method for learning rudders is happy feet. Try a little left then a little right rudder and watch the plane is in correct position, and continue a little left and right pedal. This prevents you from being lazy from tricycle gear operation and then not do the appropriate correction soon enough. You are already seeing the effects, so you compensate right away with small corrections.
Pattern speeds, flaps, and power settings

As with any new plane, it is good to become familiar with what the different power/speed/flap settings are.

With the Citabria, 70mph worked very well for the initial climb. I let the speed go up a little bit on downwind to maybe 80mph, and then bring it back to 70mph on base and final along with a reduction in the RPM to about 1500 RPM.

I heard that 70mph can work pretty well for the Decathalon too. I remember doing 75mph last time which is roughly the same.

3-point Landings

3 point tailwheel landingsA 3-point landing is an attempt to have all three wheels settle onto the runway at the same time right about when the stall horn goes off. This is the most common landing method for people to use in tailwheel trainers like the Citabria.

Make sure you are very well lined up with the runway for any small amount of crosswind. Do a foward slip early and maintain it as the winds change as you get lower. Make sure that you fly the plane in until around stall horn would go off. This makes the landing with a fairly nose high attitude; similar of course to when you are taxiing on the ground.

It helps to get the speed as close to 70mph in the Citabria as you can and trim it. Being too fast, makes the plane float and makes more back pressure needed. If you are at the right speed, you still have to ease the stick back during the flare, but it has less pressure and easier. Trimming, of course, helps your back pressure as well. When you get about the height of hangars, then start leveling out, and then flare when you are at the right height above the runway.

When you get close to touching down, you will have to watch the side of the runway with your peripheral vision in order to stay in the middle. Do not get off center from the runway and correct any difference right away. Light jabs on the rudder pedals is best; don't keep sustained pressure. The effect of pressing the rudder pedal is a bit delayed and can easily be more than necessary, so a light jab works best.

If you are not nose high enough in a 3 point at landing, the mains touch, the tail goes down from the weight behind the main wheels, angle of attack goes up, and airplane starts flying again. It looks like a bounce, but it is not from bouncing off the main wheels and is from the airplane flying again. Sometimes it is called a jounce instead because it is different. In tricycle gear, if you touch down a little early, the nose goes down from the weight being in front of the main wheels, angle of attack goes down, and the airplane stops flying. Of course if you touch down way too early in tricycle gear, you can bounce, but this would be even more severe in a tailwheel.

If the tailwheel hits a little before the main wheels this is ok, but don't make it too much before. Having the tailwheel hit slightly first is better than having the mains hit first to prevent the jounce.

Bury the stick backward once tailwheel is on the ground so the steerable tailwheel works well. Do not relax the stick to neutral or push it forward after landing.

Don't slam on the brakes after landing at least in the beginning; this will make it harder to slow down in a controlled manner; it will accent the negative stability. Keep attentive to the rudders all the time until stopped.

One thing I noticed was that the Citabria/Decathalon sit lower than a C182, so you need to flare with a lower sight picture.

I got a chance to sit the back seat a couple times. This is a little strange for a few reasons. It is hard to see the instruments. Also, when you flare, you feel your part of the plane sink because you are behind the pivot point of the plane. And when you flare, your peripheral vision for runway alignment is even more important since you can see less over the nose of the plane.

Wheel Landings

tailwheel wheel landingsA wheel landing is a landing where you attempt to have the main wheels touch first and keep the plane with the tail up while the rudder has effectiveness. Also leave the tail up until the airspeed is below stall speed. That way the plane will not try to take off again when the pitch increases when the tail is lowered.

Here is how we practiced it. Leave a little power (1300-1500RPM in Citabria), fly a shallower approach at least for starters, get in the flying low over the runway mode, don't let the plane slow down, quickly try to fly exactly level over the runway, but 1-2 feet over, then very very slowly slightly pitch down then level to inch down the runway, when you feel the wheels touch and not bounce, push the stick slightly forward, ease the power back. Bring the tail down after a couple seconds when the rudder is losing effectiveness, then go full stick back.

Flying over the runway is strange especially with enough speed to really keep flying and not flare. Pushing the stick forward is a little strange, but as long as you are slow and power off, this should be fine. Be as close to zero sink rate when initially touching the main wheels down. I flew the final at 70mph and was touching the wheels close to 60mph maybe. If it gets much slower, it tends to bounce.

If the wheel landing ends bounces, convert to a 3 point or go around. Bouncing/jouncing is very easy in the wheel landing. If you land with the slightest descent, the tail goes down, the wing flies again, and you balloon/jounce up. The key is to have the descent rate at something like inches per minute; or you effectively are nudging the plane an inch down at a time until it touches. Once again, it is easy to convert to 3 point or go around. If you convert to a 3 point, it helps to add a little power to re-establish the landing position.

Books and Websites

I looked on Amazon and looked for the best recommended book and asked some people, and ended up getting The Compleat Taildragger Pilot by Harvey S. Plourde. It seemed like a decent book. I reread a few areas after having the lessons and his comments and points about landing and takeoff are pretty good. There are some extra sections on taxiing without steerable tailwheel and landing with crosswind gear that don't apply to me, but they might to some. This other book looks good and cover others aspects of flying. I have not read it yet though. Stick and Rudder: An Explanation of the Art of Flying

I glanced around the web and found this website with taildragger information and this other site with taildragger information. Much of the information is similar between these two sites. I also found this description of landing specifically a Citabria; it is pretty good. Here is yet one more article about tailwheel training.


I think that getting a tailwheel endorsement is a good thing for pilots to get. It does not take too many hours, is a chance to try something new in flying, and is fun.

If any tailwheel pilots feel I have something a little off or could be described better, please let me know or leave a comment. I am a brand new tailwheel pilot and still comprehending how it all fits together.