On Wednesday, 14 January 2015 15:58:40 UTC, wrote:
On Wednesday, January 14, 2015 at 9:35:43 AM UTC-5, mt wrote:
Our 235 hp Pawnee has again some cracks in the tail tubing. One of them is on the bottom of the vertical member where rudder hinges are welded. The crack is between the lowest and the middle hinges.

As a glider instructor and tow pilot (over 35 years) I don't see why we should keep "boxing the wake", as part of glider pilot training. Having said that, contrary to some opinions in my club, I don't believe aggressive boxing the wake is the only contributing factor in our costly maintenance issues. FYI, our Pawnee has been hangared at least in the past 20 years!

What are your experiences:
1- with Pawnee tail fatigues
2- cause of repeated cracks, method of usage
3- methods of fixing them better next time
4- what contributtes to more stress on the tail tubing: hitting rudder stops in everyday operations, boxing the wake, hard landings, or rope breaks (weak link about 1250 lb).
Many Thanks,
C1

Boxing the wake is essential to
learning how properly control a glider on tow.
I box the wake on virtually every tow, just to keep my skills sharp.

Reply from Ian Strachan, UK glider and power pilot.

I was a glider and power (civil and military) instructor for 40 years, now retired from instructing but still flying gliders and tow planes at Lasham in the UK. In my gliding career I was Chief Instructor at two UK clubs and in the military instructed on single, twin and four engined types.

When I started instructing in the 1960s there was no such thing as "boxing the wake". Before sending someone solo on aerotowing you ensured that the guy could get back to the central tow position from being out of position left and right, up and down.

This was done by the instructor flying gradually and smoothly to the out-of-position position and handing over to the student to recover to the "central" tow position. The emphasis was on smooth, gradual and safe use of the controls, not rough and unneccessary control applications. The dangers of overcontrol leading to overshooting the central two position and the risk of oscillation were discussed and demonstrated. In the UK the standard tow position is "high tow" above the wake and part of pre-solo instruction was to show the wake and make sure that the pupil could get back into high tow position from a wake encounter. We did not deliberately teach the "low tow" position itself, at least until a guy had already been solo on aero tow.

When the fashion started for so-called "boxing the wake", I was horrified because many instructors took it as a licence to be rough with the controls and IMHO took it too far. As a tug pilot I looked at what was happening behind me as a demonstration of poor airmanship and probably off-putting to many pupils. A long-term instructor often forgets that some pupils are quite nervous. Pilots who have been instructors for many years need to be reminded of the basic principles such as gradual and sympathetic demonstration and then student practice of the various skills, without taking things too far because the instructor has lost the ability to put him/herself in the place of the student.

When instructing, I refused to Box the Wake but continued as I had done before. I don't think my aero tow students had any problem when they went solo on tow.

Clearly C1's claim that boxing is "essential", is not right. Unless you regard what I describe above as "gentle boxing".

I guess it all turns on what you mean by "boxing".

The problem was that once it started, there was far to much "aggressive boxing" by instructors who maybe were trying to show how clever they were (and annoying tow pilots like me) and had IMHO fogotten one of the basic tenets of instruction which is "not to do the advanced course before the basic", or not to demonstrate running before the pupil can walk, if you see what I mean. I have seen instructors take it too far, for instance breaking the rope/weak link or even arriving just off the tug wing tip with a huge loop in the rope.

I would hope that we could agree that "aggressive boxing" during pre-solo aero tow instruction is unneccessary.

IMHO it is a poor instructional technique which is not necessary before safely sending a student solo on tow. Even on post-solo check rides, I see no need for it and suggest that a less "agricultural" approach should be used.. An aero tow is not an aerobatic and controls should be used gradually, not over-used when it is not necessary.

Ian Strachan
Lasham Gliding Centre, UK