North American T-6
Instructing in the T-6
by Burke Mees
Written December 2019; Published by the AEHS 15 May 2024
North American T-6 |
As an instructor, I have a great appreciation for the North American T-6. Supposedly the airplane was designed to be difficult to fly in the interest of developing pilots’ abilities, but I’d take that idea a step farther and suggest that its difficult nature was intended to support specific training objectives. The airplane’s particular flight characteristics call attention to some of the central topics in the tailwheel checkout, and by shining a spotlight on these topics the airplane supports the efforts of the instructor. We end up working as a team; I explain how things work and the airplane drives my points home. By its very nature, the T-6 helps the pilot confront some important tailwheel principles and engage them to proficiency. |
Rudder Inputs And Timing
I’d describe the T-6 as especially squirrelly in yaw, but also very responsive in steering and I’ve found this combination to be effective for getting a pilot used to the rhythm and timing of rudder inputs appropriate to tailwheel airplanes. I first came to appreciate this combination instructing in a Luscombe, and now I’ve seen it work to good effect in the T-6. The exaggerated instability forces us to make frequent corrections while good steering authority forces us to judiciously avoid over-controlling those corrections. This gives equal emphasis to the initiation and removal of rudder inputs, and conditions a pilot to make more frequent smaller corrections rather than fewer, larger ones.
Over-controlling the rudder is a usually a problem for new tailwheel pilots and to put that topic in perspective, I explain how the nature of rudder corrections differs between nosewheel and tailwheel airplanes; In a nosewheel airplane you can hold a rudder correction until you’re where you want to be, then release the input and the stable airplane is content with its new heading. In a tailwheel airplane, if you hold a rudder correction until you reach the desired heading, the nose will swing through the centerline, at which point the instability takes over and creates a pressing need for an opposite correction. To stay ahead of the airplane, you have to release your initial correction before it fully achieves its objective.
The reference here is to promptly make a rudder correction at the first indication that you’re not straight, but then remove that correction as soon as it begins to take effect. When the airplane first responds to the correction and the nose starts to swing towards center, that’s your cue to back off and neutralize the rudder before things go too far. The T-6 is especially effective at illustrating this concept.
This explains why slower, longer-duration rudder corrections are appropriate for nosewheel airplanes while fast, short-duration jab-and-release motions are appropriate in tailwheel airplanes. In nosewheel airplanes, we make rudder inputs by reference to the position of the nose, but in the T-6 we also make corrections with reference to the motion of the nose. This principle of making corrections based on motion also applies to other unstable scenarios. For example suppressing divergent porpoise in a hull seaplane involves short jab-and-release elevator inputs in response to the motion, rather than the position of the bow.
I can explain all this, but the T-6 gets my points across. When I point out that a pilot is holding rudder corrections too long, the T-6 makes it clear that this is a problem. When I tell a pilot to release rudder corrections as soon as they begin to take effect, the T-6 clearly demonstrates that this is sound advice. The rudder corrections required by the T-6 help a pilot internalize this important tailwheel principle to the point that it becomes raw instinct.
Wing Lift on Takeoff and Landing
Managing wing lift throughout the takeoff and landing is an important tailwheel topic, but in some airplanes the relevance doesn’t become fully apparent until we get into adverse conditions such as gusty crosswinds. Even in the best of circumstances the T-6 is especially sensitive to proper management of wing lift and the airplane does us a service by highlighting this topic.
Tailwheel airplanes usually handle best when their weight is either fully supported by the wings, or fully supported by the wheels, and they tend to be less friendly in that in-between area where the weight resides partially in both places. When the weight of the T-6 is allowed to wallow somewhere between the wings and the wheels, you can find yourself in an unsteady region where the airplane is noticeably more difficult to control. This aerodynamic morass can be avoided by managing angle of attack to put the weight where you want it, and making a clean transition on takeoff and landing that avoids loitering in the in-between area.
On the takeoff run, as the airplane builds speed I lift the tail to reduce the angle of attack and prevent the premature creation of wing-lift. This keeps the wings unloaded, holds weight on the wheels and assures a firm grip on the runway. When there is sufficient airflow for flight, I raise the angle of attack to promptly shift the full weight onto the wings.
When it comes to a wheel landing, the same principle applies, but in reverse order. After touching down slightly tail-low with flying speed, a gentle nudge forward on the stick serves to unload the wings, plant weight on the wheels and put the airplane in the better-behaved range. If the touchdown isn’t perfectly smooth, then unloading the wings also prevents a bounce which, if it doesn’t launch the plane back into the air, can lift it into the unsteady region. After the initial touchdown I keep the wings unloaded until the plane decelerates to the point that lowering the tail (increasing the angle of attack) doesn’t produce any unwanted lift. Neglecting to unload the wings on touchdown, or lowering the tail prematurely on the rollout can lighten the weight on the wheels and put you in this awkward area.
In the case of a three-point landing, taking the wing all the way to the stall assures a clean transition from weight entirely on the wings to weight entirely on the wheels. A premature three-point landing that touches down with excess speed above the stall can bounce you into this awkward area where there is still some lift on the wings.
This in-between area is awkward but not untenable–the airplane still controllable, it just requires more assertive supervision. Wrestling with the airplane in this region is good sport, but managing wing lift to avoid it makes life easier and the T-6 clearly illustrates this point. When the airplane starts to get unruly and I tell the student to ‘plant the weight on the mains’, the improved behavior is readily apparent and they get the point. When a student plunks down a wheel landing and fails to suppress a light bounce, the resulting bad behavior makes the case for unloading the angle of attack on touchdown. The concept of unloading the wings after a wheel landing is especially helpful in strong or gusty crosswinds since it gives the tires a firm grip on the pavement.
Crosswinds
Even light crosswinds that can be ignored in other airplanes make themselves felt in the T-6, and stronger crosswinds require assertive treatment. Despite its sensitivity to crosswinds, the T-6 has the right tools for dealing with them in the form of an effective air-rudder and large authoritative ailerons with a lot of adverse yaw.
The T-6 provides a clear illustration of how adverse aileron yaw can be used to mitigate the nuisance of weathervaning in a crosswind. Weathervaning pulls the nose into the wind, but deflecting aileron into the crosswind pulls the nose away from the wind, which works to even things out and noticeably improves control.
The significant adverse yaw of the T-6 makes it clear that, for better of for worse, this is a force to be reckoned with. Deflecting aileron into a crosswind makes life noticeably easier, failing to use aileron at all is a missed opportunity, and deflecting aileron in the wrong direction, away from the wind, causes problems that have contributed to mishaps.
This important point tends to get lost in the age of modern nosewheel airplanes where the effects of both weathervaning and adverse yaw are less pronounced. By now at least a couple generations of pilots have been taught that the only reason we apply aileron into a crosswind to keep the wind from lifting the wing. That’s a relevant consideration in strong winds, but the T-6 makes it clear that the more immediate reason to use aileron has to do with tapping into adverse aileron yaw to improve control. Less sensitive airplanes are less suited to making this point, but the T-6 provides a clear illustration even in light winds. When someone is struggling with a crosswind and I suggest leaning into it with some aileron, they see immediate results and the point gets across.
Good Cop, Bad Cop
I’ve enjoyed my association with the T-6 and sometimes my partnership with the airplane resembles a good-cop bad-cop routine. I get to be the nice guy who calmly explains how things work and the airplane beats the student around until they ‘get it’. The airplane calls attention to the relevant topics, it coerces the student into cultivating good technique and it discourages bad habits through negative reinforcement. By the end of a T-6 checkout, the airplane will make sure you have a good grasp of the tailwheel topics described above. If you’re new to the T-6 then the corollary applies- going into a checkout with a good understanding of these same topics paves the way for success in the T-6.
Was the T-6 was meant to have these characteristics that I’ve found to be so useful? I suspect so. There were some pretty sharp people designing airplanes in the 1930s who understood how different variables affect handling and I have no doubt they could call on that knowledge to achieve a desired result. I don’t think it’s any coincidence that other training airplanes such as the Boeing Stearman and Vultee BT-13 have the characteristics appropriate for tailwheel formation, while transport airplanes from that era usually have the easier handling qualities appropriate to working airplanes. I’m convinced the T-6 was intentionally designed to be ‘the pilot maker’, and it continues to be effective in that role eight decades later.
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