Boxing the wake cracks Pawnee tail tubings or long term fatigue?

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

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. If your tow plane can't handle this stress, it needs some structural reinforcement.

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. If your tow plane can't handle this stress, it needs some structural reinforcement.

Boxing the wake might teach essential skills but if it's doing damage to a tow plane, why on earth should we continue the practice. Develop other training methods to teach that skill set. It's similar to the requirement in the Powered Aircraft training which requires a commercial pilot applicant to perform a "Lazy Eight". I'm a CFI and I can tell you that a lot of money is wasted teaching that maneuver for the commercial check ride. I'd bet that darn few of those commercial students can perform that maneuver 6 months after the check-ride. It's nothing more than a CFI meal ticket.

On Wednesday, January 14, 2015 at 11:16:25 AM UTC-5, wrote:
Boxing the wake might teach essential skills but if it's doing damage to a tow plane, why on
earth should we continue the practice. Develop other training methods to teach that skill set.

Students ask me "Why do we practice the box the wake maneuver?"
It takes all of my effort as an instructor to suppress the smart-alec answer:
"Because the FAA requires us to."
Which inevitably leads to the next question of: "Why does the FAA require us to?"
"Because the FAA requires us to."

Does it hone the skill of precise flying while on tow? Yes.
Does it teach people how to move around behind the tow plane? Yes.
Does it teach people "how much" they can get away with w.r.t. positioning behind the towplane? Yes.

When I went to Switzerland, I found that boxing the wake is not a required item for their flight instruction. It was more done as a demonstration to understand the limits of how far a glider can get out of position.

They also didn't practice forward slips on final to lose altitude. They saw this practice as out-of-touch for use with modern gliders. "Sure it's a useful skill... if you're flying old museum pieces like you do in the United States!" I think that might be a jab against Schweizers.

How many other countries, besides the US, require the box-the-wake maneuver?

Piet, I don't know where you got your information, but forward slip and also boxing the wake (called "extreme Schleppfluglagen") are both required maneuvers in glider training in Switzerland.

On Wednesday, January 14, 2015 at 12:03:10 PM UTC-5, wrote:
Piet, I don't know where you got your information, but forward slip and also boxing the wake (called "extreme Schleppfluglagen") are both required maneuvers in glider training in Switzerland.

Granted, I wasn't going for a rating there, so I didn't go through the whole training program. Maybe the instructor was just de-emphasizing the concepts.

On Wednesday, January 14, 2015 at 9:16:25 AM UTC-7, wrote:

Boxing the wake might teach essential skills but if it's doing damage to a tow plane, why on earth should we continue the practice.

Because it teaches ESSENTIAL skills.

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

I have been instructing gliders for about 27 years, and for me the boying the wake excercise is essential during pre-solo training.
Part of it is to show the student the limits of possible positioning behind the tug (and on the lateral positions of the box, the tug pilot will have to use quite some rudder to keep going straight), and especially to show the point beyond which immediate release is mandatory on high positions.
Low position (well below the wake) is something the student needs to learn for descent and approach on tow anyways.

Having said that, there is no aggressive maneuvring involved at all, with me talking the students through the excercise. Changing positions is done gradually all the way through the excercise, with constant tension on the rope.

It usually is an excercise which is flown once with the student, and at some point when he is at a level where I don't have to interfere anymore on a normal tow.

Bert TW

I don't understand the logic of boxing the wake as a training exercise. Why teach students how to move from one undesirable out of position scenario directly to all the other possible out of position scenarios ? When is that going to be useful in real flying? It makes no sense to me.

John Galloway