Tailwheel Conversion


Decades ago, when nosewheel aircraft were a rarity, everyone learned to fly on a tailwheel aircraft, usually of tube and fabric construction.  Then, the nosewheel came along.  The Cessna 150/152/172 series of aircraft were produced in phenomenal numbers and it’s not hard to see why.  With their all-metal construction they could be economically tied down outside – unlike the old fabric taildraggers – and with a nosewheel, they were much easier to land than tailwheel aircraft.  There aren’t many of those old tube & fabric taildraggers left, because the cost to restore one is more than it is worth afterwards.


A very good question is why, given their poor ground handling characteristics, that anyone would still produce a tailwheel aircraft.  Or even want to fly one!


The reason is very simple – propeller clearance.  A tailwheel aircraft has its nose up in the air, and that means more space between the ground and the tips of the propeller blade.  So, if you want to operate off unpaved runways, or you want a larger diameter prop (eg aerobatic aircraft that want more thrust) you probably want a tailwheel aircraft.  Also, if you learn to fly tailwheel, it opens the door for you to fly all sorts of interesting warbird and antique aircraft.  It will also improve your stick & rudder skill.


Anyways, the actual reason a nosewheel aircraft is so easy to land, is because its center of gravity – technically, its center of mass – is ahead of the main gear.  If it wasn’t, it would flop onto its tail when it’s parked on the ramp, and it doesn’t.  The effect of the center of mass ahead of the main gear, is that if you get little sideways rolling down the runway, the center of mass pulls the aircraft straight again.  It’s stable, so you can pretty much leave your feet flat on the floor during the rollout.  Seriously.  Use of the rudders is optional.


However, a tailwheel aircraft has it’s center of mass behind the main gear.  If it didn’t, it would fall on its nose when it’s parked, and it doesn’t.  Now, the problem with the center of mass behind the main gear is that if you get a little crabbed on the runway, the center of mass drives the main gear to a greater angle from the centerline.  This is very bad – it’s divergent!  A little problem becomes a big problem unless the pilot does the “right thing” with the rudder pedals.


In the air, there is absolutely no difference between a nosewheel and a tailwheel aircraft.  They fly exactly the same.  Don’t believe the nonsense about the tailwheel having less drag.  I don’t believe it’s more than a mile per hour at the most.  I personally and subjectively think tailwheel versions of aircraft (eg RV-7 vs RV-7A) look far better than the nosewheel versions, but remember, opinions are like rear ends – everyone has one, and it’s not considered polite to shove yours in someone else’s face.


I digree.  When the tires touch the ground – and the worst surface for a taildragger is a dry, paved runway – a nosewheel and tailwheel aircraft behave totally differently.  A nosewheel aircraft is inherently directionally stable when the tires are on the pavement, making the use of the rudders pretty much optional.  Really.  However, a tailwheel aircraft is inherently directionally UNSTABLE when the tires are on the pavement, because of the need for the pilot to “balance” the direction of the aircraft with his feet on the rudder pedals.


The conclusion from the above – and if you learn nothing else from reading this – is that when things start to go wrong during a tailwheel aircraft landing, apply FULL POWER, get some directional control with the tailfeathers from the slipstream, get some airspeed and above all get some altitude.  All you need is a foot or two of height, and you are safe again.  Just try not to take out the runway lights, if you can avoid it.


But I’m getting ahead of myself.  Transport Canada Aviation in the FIG refers to the Learning Effect of Primacy, which says to “teach it right the first time”.  Unfortunately, this doesn’t happen these days, because nearly everyone learns to fly on a nosewheel aircraft, which teaches them the instinct that they can leave their feet flat on the floor when something goes wrong.  Sigh.


The result of this is that it generally takes twice as long for people to convert from nosewheel to tailwheel, than it does to teach them to fly tailwheel in the first place.


When my son was learning to fly, I forbade him from flying anything with a nosewheel. 


I made an exception for the C421 and L39 because of the unique things they could teach him.  But he could fly any taildragger in the hangar – and for that matter, the airport – that he could get his hands on.  And I encouraged him to fly as much as he could.  I firmly believe that any pilot with less than 1,000 hours should fly at least once, preferably twice every day, weather permitting.  That’s how you get good at something – an insane, OCD amount of practice, practice, practice.  But I digress again.


Exactly how do you keep a taildragger straight, when the tires are on a dry paved runway?  Well, during takeoff it’s generally pretty easy, because your speed is increasing and you have the prop slipstream over the tail feathers, increasing their effectiveness.  Some right rudder will generally the job, if you are behind a western engine such as a Lycoming or Continental.


However this is not the case during landing, when the power is at idle and the rudder is rapidly losing effectiveness as the speed decreases.  Progressively more rudder may be required to keep an aircraft straight during the rollout.


It’s really important to remember with a tailwheel aircraft to NOT let the tires touch the (dry, paved) runway if there is ANY crab.  The aircraft must be pointed in the direction it is moving, before you allow the tires to touch the runway.  If the aircraft touches down with even 5 degrees of crab, it will launch itself towards the side of the runway, and it’s up to the pilot fix that.  More about that below.


However, if you can touch a tailwheel aircraft down perfectly aligned with its direction of travel, it will continue straight down the runway unless something disturbs it, like a gust of crosswind or you poke a rudder.  This is an important detail to remember.


Sooner or later, the taildragger is going to head for the side of the runway, and all that stands between you and a phone call to the TSB is your feet.  You need to learn the Three Step.  Yes, I know white men can’t dance, but you can learn.  Honest.


Let’s say the aircraft heads for the left ditch.  Quite reasonably, you step on the right rudder – First Step - but you will press it for too long, and it will inevitably head for the right ditch, possibly at a greater (worse) angle than the first dart for the left ditch.  You are now overcontrolling, which is bad.  Oscillations are no fun in aviation.


How to avoid this, is BEFORE the aircraft gets parallel with the runway, is to get off the left rudder and press the right rudder, not as much as you pressed the left rudder.  This is the Second Step.


Generally, you will need one more slight tap on the right rudder – Third Step – to cancel out the effect of the Second Step (left rudder).  If you’re really good, you won’t need the Third Step.


Let’s review what happened.  The aircraft went left, and we pressed on the right rudder, then slightly before it was back to being aligned with the runway, we then pressed the left rudder, and finally one more tap on the right rudder.  That’s the Three Step.


You will almost certainly NOT be on the runway centerline, but that’s ok.  It’s very important to spend a couple seconds, stablized parallel to the centerline.  Only after all the oscillations in yaw have disappeared, do you then slowly apply a 5 degree correction back to the runway centerline.  You want a gradual movement laterally back to the centerline, so that you won’t have another dangerous wiggle when you try to straighten out on the runway centerline again.


This is how I teach someone to control a tailwheel aircraft.  We taxi up and down a quiet runway – often in the process burning off a tailwheel, but that’s just the cost of doing business, keep a built-up spare – slowly at first, and we play the “wind game”, which I shamelessly stole from Budd Davisson. 


After the student establishes the aircraft on the runway centerline, I press a rudder hard enough to angle it towards the runway edge.  The student then practices the three step as above.  The more he practices it, the better he will get.  As he improves, I increase the taxi speed – I control the throttle – until the student has a hope at controlling the aircraft at the fast taxi speed after touchdown.


Too often I see incompetent tailwheel instructors jump into the circuit with students, and they have harrowing experiences after touching down, with the student woefully behind the aircraft as they bounce back into the air.  What a waste of time and money.  You give me a tailwheel student and in one or two lessons of the “wind game” taxiing, and he will be far ahead of someone who hasn’t spent the time learning to taxi.  Remember, a tailwheel aircraft behaves the same in the air – it’s only on the ground that it behaves differently than a nosewheel aircraft, so why not learn to control it on the ground?


One really important point I want to make.  Everyone obsesses about a greaser landing, which is actually completely useless.  You won’t hurt the airplane by dropping it in from a foot.  Or even two.  What will hurt a taildragger is if you don’t keep it straight on the runway.  I know of taildraggers that have experienced +4G and +5G landings but they were completely unhurt because they were kept straight. 


Obviously you want to minimize these sorts of hard landings – remember to use FULL POWER if you don’t like what you’ve got during a tailwheel landing – but please do remember that it’s far more important to keep it straight, than to get a greaser, to avoid hurting the airplane.  IMHO the quality of a tailwheel landing can be objectively measured by the degrees of yaw experienced during the landing – not how gentle the touchdown was.


See next tailwheel training article – Wheel Landings.



acboyd@gmail.com  Sept 2011