Puchacz shock cord (bungee) failure

This weekend one of the bungee cords that serves as the shock absorving
element of the main landing gear of our SZD 50 Puchacz was found to be
broken. The symptom was a weird noise coming out the main wheel area
while the plane was taxiing back for a relaunch. The plane had a
uneventful landing moments before. Upon inspection the broken bungee
was aparent at the brake side of the main wheel. Seems that the brake
lever that goes up through the landing box has caused a premature
failure of the cord by repetitive attrition. Therefore, I advise all
Puchacz operators to inspect for the status of the bungees specially
the left one (looking tail to nose) each flight day for premature
wearing around the brake lever.
Also, the Puchacz can land with two people on just one bungee and
nobody will notice it...as long you grease in....

Another thing you might like to consider is doing away with the Puchacz
original mainwheel & brake which have two severe irritations (in addition to
the one you describe):
1. the brake is a bugger to adjust and a bugger to keep operational in a
dusty & gritty environment, and
2. the valve for the tyre is located inside the mainwheel hub which is so
inconvenient that it is a disincentive to people checking & pumping the tyre
pressure up when required.

You can overcome both these aspects by installing the hydraulic disc braked
wheel kit for the Puchacz from Tost which we have found to be a really good
mod to do. The only hassle we have had with it in four years is that
recently we lost presure due to leakage at the master cylinder to brake hose
junction. This was almost certainly due to the brake hose end continuously
flexing as the undercarriage moves. The fix we think is to install a
support to hold the start (ie the master cylinder junction end) of the brake
hose very firmly and resist the flexing.

While I am contributing some ideas to others, perhaps someone out there in
Puchacz land knows and can advise what the fix procedure is when you get to
the stage where the freeplay at the tip of the horizontal stabiliser exceeds
limits?

Cheers
Roger Druce, Australia

wrote in message
oups.com...
This weekend one of the bungee cords that serves as the shock absorving
element of the main landing gear of our SZD 50 Puchacz was found to be
broken. The symptom was a weird noise coming out the main wheel area
while the plane was taxiing back for a relaunch. The plane had a
uneventful landing moments before. Upon inspection the broken bungee
was aparent at the brake side of the main wheel. Seems that the brake
lever that goes up through the landing box has caused a premature
failure of the cord by repetitive attrition. Therefore, I advise all
Puchacz operators to inspect for the status of the bungees specially
the left one (looking tail to nose) each flight day for premature
wearing around the brake lever.
Also, the Puchacz can land with two people on just one bungee and
nobody will notice it...as long you grease in....

Roger Druce wrote:
Another thing you might like to consider is doing away with the Puchacz
original mainwheel & brake which have two severe irritations (in addition to
the one you describe):
1. the brake is a bugger to adjust and a bugger to keep operational in a
dusty & gritty environment, and
2. the valve for the tyre is located inside the mainwheel hub which is so
inconvenient that it is a disincentive to people checking & pumping the tyre
pressure up when required.

You can overcome both these aspects by installing the hydraulic disc braked
wheel kit for the Puchacz from Tost which we have found to be a really good
mod to do. The only hassle we have had with it in four years is that
recently we lost presure due to leakage at the master cylinder to brake hose
junction. This was almost certainly due to the brake hose end continuously
flexing as the undercarriage moves. The fix we think is to install a
support to hold the start (ie the master cylinder junction end) of the brake
hose very firmly and resist the flexing.

While I am contributing some ideas to others, perhaps someone out there in
Puchacz land knows and can advise what the fix procedure is when you get to
the stage where the freeplay at the tip of the horizontal stabiliser exceeds
limits?

Cheers
Roger Druce, Australia

wrote in message
oups.com...
This weekend one of the bungee cords that serves as the shock absorving
element of the main landing gear of our SZD 50 Puchacz was found to be
broken. The symptom was a weird noise coming out the main wheel area
while the plane was taxiing back for a relaunch. The plane had a
uneventful landing moments before. Upon inspection the broken bungee
was aparent at the brake side of the main wheel. Seems that the brake
lever that goes up through the landing box has caused a premature
failure of the cord by repetitive attrition. Therefore, I advise all
Puchacz operators to inspect for the status of the bungees specially
the left one (looking tail to nose) each flight day for premature
wearing around the brake lever.
Also, the Puchacz can land with two people on just one bungee and
nobody will notice it...as long you grease in....



Well, I can't resist......you all know that there is not very far from
Puchacz to Ruchacz....just a letter....

When we got our original Puchacz about 15 years ago
the Polish bungees lasted about 3/6 months. We then
sourced them from a UK supplier and had them changed
routinely at annual C oA inspection. The outer braiding
on bungees is an integral part of the structure not
just to make it look nice, the rubber is pre-tensioned
and the braiding holds holds the pre-tension, so if
it is damaged the bungee has failed.
There are bump stops on the undercarriage, so it will
only go so far.
The original brake, as well as being useless also had
a tendancy to stick on, ( I saw one wheel actually
explode as it was being towed, and it wasn't known
that the brake had stuck on, and it generated considerable
heat), so we also changed to Tost wheels, but not
hydraulic.
No experience of the tailplane excessive play, but
assume it is wear in the bush in the fin, so presumeably
replace it.
Dave






At 16:24 30 June 2006,
wrote:

Roger Druce wrote:
Another thing you might like to consider is doing
away with the Puchacz
original mainwheel & brake which have two severe irritations
(in addition to
the one you describe):
1. the brake is a bugger to adjust and a bugger
to keep operational in a
dusty & gritty environment, and
2. the valve for the tyre is located inside the
mainwheel hub which is so
inconvenient that it is a disincentive to people checking
& pumping the tyre
pressure up when required.

You can overcome both these aspects by installing
the hydraulic disc braked
wheel kit for the Puchacz from Tost which we have
found to be a really good
mod to do. The only hassle we have had with it in
four years is that
recently we lost presure due to leakage at the master
cylinder to brake hose
junction. This was almost certainly due to the brake
hose end continuously
flexing as the undercarriage moves. The fix we think
is to install a
support to hold the start (ie the master cylinder
junction end) of the brake
hose very firmly and resist the flexing.

While I am contributing some ideas to others, perhaps
someone out there in
Puchacz land knows and can advise what the fix procedure
is when you get to
the stage where the freeplay at the tip of the horizontal
stabiliser exceeds
limits?

Cheers
Roger Druce, Australia

wrote in message
oups.com...
This weekend one of the bungee cords that serves
as the shock absorving
element of the main landing gear of our SZD 50 Puchacz
was found to be
broken. The symptom was a weird noise coming out
the main wheel area
while the plane was taxiing back for a relaunch.
The plane had a
uneventful landing moments before. Upon inspection
the broken bungee
was aparent at the brake side of the main wheel.
Seems that the brake
lever that goes up through the landing box has caused
a premature
failure of the cord by repetitive attrition. Therefore,
I advise all
Puchacz operators to inspect for the status of the
bungees specially
the left one (looking tail to nose) each flight day
for premature
wearing around the brake lever.
Also, the Puchacz can land with two people on just
one bungee and
nobody will notice it...as long you grease in....



Well, I can't resist......you all know that there is
not very far from
Puchacz to Ruchacz....just a letter....

David Salmon wrote:
When we got our original Puchacz about 15 years ago
the Polish bungees lasted about 3/6 months. We then
sourced them from a UK supplier and had them changed
routinely at annual C oA inspection. The outer braiding
on bungees is an integral part of the structure not
just to make it look nice, the rubber is pre-tensioned
and the braiding holds holds the pre-tension, so if
it is damaged the bungee has failed.
There are bump stops on the undercarriage, so it will
only go so far.
The original brake, as well as being useless also had
a tendancy to stick on, ( I saw one wheel actually
explode as it was being towed, and it wasn't known
that the brake had stuck on, and it generated considerable
heat), so we also changed to Tost wheels, but not
hydraulic.
No experience of the tailplane excessive play, but
assume it is wear in the bush in the fin, so presumeably
replace it.
Dave






At 16:24 30 June 2006,
wrote:

Roger Druce wrote:
Another thing you might like to consider is doing
away with the Puchacz
original mainwheel & brake which have two severe irritations
(in addition to
the one you describe):
1. the brake is a bugger to adjust and a bugger
to keep operational in a
dusty & gritty environment, and
2. the valve for the tyre is located inside the
mainwheel hub which is so
inconvenient that it is a disincentive to people checking
& pumping the tyre
pressure up when required.

You can overcome both these aspects by installing
the hydraulic disc braked
wheel kit for the Puchacz from Tost which we have
found to be a really good
mod to do. The only hassle we have had with it in
four years is that
recently we lost presure due to leakage at the master
cylinder to brake hose
junction. This was almost certainly due to the brake
hose end continuously
flexing as the undercarriage moves. The fix we think
is to install a
support to hold the start (ie the master cylinder
junction end) of the brake
hose very firmly and resist the flexing.

While I am contributing some ideas to others, perhaps
someone out there in
Puchacz land knows and can advise what the fix procedure
is when you get to
the stage where the freeplay at the tip of the horizontal
stabiliser exceeds
limits?

Cheers
Roger Druce, Australia

wrote in message
oups.com...
This weekend one of the bungee cords that serves
as the shock absorving
element of the main landing gear of our SZD 50 Puchacz
was found to be
broken. The symptom was a weird noise coming out
the main wheel area
while the plane was taxiing back for a relaunch.
The plane had a
uneventful landing moments before. Upon inspection
the broken bungee
was aparent at the brake side of the main wheel.
Seems that the brake
lever that goes up through the landing box has caused
a premature
failure of the cord by repetitive attrition. Therefore,
I advise all
Puchacz operators to inspect for the status of the
bungees specially
the left one (looking tail to nose) each flight day
for premature
wearing around the brake lever.
Also, the Puchacz can land with two people on just
one bungee and
nobody will notice it...as long you grease in....



Well, I can't resist......you all know that there is
not very far from
Puchacz to Ruchacz....just a letter....

Hey if anyone needs a set of Bungee cords I have a set of new ones! I also have a Puch that I would like to sell, Part or all. Rt wing is good Lt wing has a little damage, horizontals are good, Fuse has a lot of good parts. I need to move this out of a hanger so it will all go cheap!!!!!!