Hydraulic "Transparancy"?

[Winnie]

For Magseal and other who may know:
What is it really?
From what I understood in the POH it is a system to "warn" the pilot of possibly overstressing the machine, by stiffening up the controls in large angles of bank and or with sharp pullups? I remember an instance in Norway a couple of years back, when the pilot banked really steep, and almost lost control, and the AAIB-N atributed that to "transparency" and inadequate knowledge of the phenomenon, can anybody explain?

Thank you very much!

 

[Winnie]

For Magseal and other who may know:
What is it really?
From what I understood in the POH it is a system to "warn" the pilot of possibly overstressing the machine, by stiffening up the controls in large angles of bank and or with sharp pullups? I remember an instance in Norway a couple of years back, when the pilot banked really steep, and almost lost control, and the AAIB-N atributed that to "transparency" and inadequate knowledge of the phenomenon, can anybody explain?

Thank you very much!

 

[407 Driver]

Winnie, I can't explain it as good as MagSeal, but it's more to do with the flight loads from the M/R system overpowering the Hydraulic system....giving the pilot the feel of locked controls. It generally happens in higher G situations, ie turns.

I only had it happen once in my Astar days, not a pleasant experience. The key to recovering is to level the aircraft and / or reduce collective pitch. ( with very stiff controls).

 

[407 Driver]

Winnie, I can't explain it as good as MagSeal, but it's more to do with the flight loads from the M/R system overpowering the Hydraulic system....giving the pilot the feel of locked controls. It generally happens in higher G situations, ie turns.

I only had it happen once in my Astar days, not a pleasant experience. The key to recovering is to level the aircraft and / or reduce collective pitch. ( with very stiff controls).

 

[Jammed left]

It also happens during extreme turbulence. The way it was explained to me is exactly as described above. The load on the M/R exceeds the capabilities of the servo. The obvious solution to get out of the transparency is to reduce the load on the servos - the few times I''ve had it, it was fairly easy to get out of- pushing down on the stiff collective wasn''t too hard, and control is restored.

The key to preventing it from becoming a serious problem is to understand that it occurs in high disk loading situations. I think if you aren''t into high speed, low altitude, high g maneuvers, there aren''t too many situations (but maybe a select few) where it would be too much of a problem to deal with.

If there are some situations / experiences where it did become an issue, I''d be interested in hearing them

cheers

 

[Jammed left]

It also happens during extreme turbulence. The way it was explained to me is exactly as described above. The load on the M/R exceeds the capabilities of the servo. The obvious solution to get out of the transparency is to reduce the load on the servos - the few times I''ve had it, it was fairly easy to get out of- pushing down on the stiff collective wasn''t too hard, and control is restored.

The key to preventing it from becoming a serious problem is to understand that it occurs in high disk loading situations. I think if you aren''t into high speed, low altitude, high g maneuvers, there aren''t too many situations (but maybe a select few) where it would be too much of a problem to deal with.

If there are some situations / experiences where it did become an issue, I''d be interested in hearing them

cheers

 

[407 Driver]

It may have become an issue in Canmore AB about 15 years ago. A fully loaded 350B crashed on Christmas day, all 6 on board were killed. The aircraft''s rear stinger made a 400'' mark in the snow prior to impact. A video camera on board showed that the aircraft conducted a fast and low ridge crossing. The aircraft may have experienced lee-side turbulence, lost HYD control, and was in a position that the pilot could not safely reduce collective. This pilot WAS NOT known as a cowboy, he may have simply been caught by this phenomonon.

On my one and only time in "transparency" I was in a
B model, AUW of around 4200#, gently circling a spot fire at 4,000'' +30c when the controls locked....no more than 15 degs of bank at 70 Kts.

 

[407 Driver]

It may have become an issue in Canmore AB about 15 years ago. A fully loaded 350B crashed on Christmas day, all 6 on board were killed. The aircraft''s rear stinger made a 400'' mark in the snow prior to impact. A video camera on board showed that the aircraft conducted a fast and low ridge crossing. The aircraft may have experienced lee-side turbulence, lost HYD control, and was in a position that the pilot could not safely reduce collective. This pilot WAS NOT known as a cowboy, he may have simply been caught by this phenomonon.

On my one and only time in "transparency" I was in a
B model, AUW of around 4200#, gently circling a spot fire at 4,000'' +30c when the controls locked....no more than 15 degs of bank at 70 Kts.

 

[4961]

It's worse in the B or D compared to the rest of the type. Not much fun if your close to the ground.

 

[4961]

It's worse in the B or D compared to the rest of the type. Not much fun if your close to the ground.

 

[407 Driver]

Why would that be 4961? Those little green blades are so much smaller than the 355 grey blades? Is it a different HYD pump on the BA and larger?

 

[407 Driver]

Why would that be 4961? Those little green blades are so much smaller than the 355 grey blades? Is it a different HYD pump on the BA and larger?

 

[I FLY]

I had it happen to me in a gradule descent from 4000'' with a full load of siesmic boys in a B1. I had about 80% TQ, with AS at about 120KT and it was a turbulant and about a 500 to 1000 foot ROD with the turbulance. dropped the collective as it happened and it pushes to the right and quick.

 

[I FLY]

I had it happen to me in a gradule descent from 4000'' with a full load of siesmic boys in a B1. I had about 80% TQ, with AS at about 120KT and it was a turbulant and about a 500 to 1000 foot ROD with the turbulance. dropped the collective as it happened and it pushes to the right and quick.

 

[4961]

The smaller blades on the B are the problem (blue for the B and D grey for all the rest). The hydraulic systems are all the same from the pump to the servos. It seems that the smaller blades have a harder time with the forces and transfer it to the servos. Get up to altitude in a loaded B and you''ll feel some feedback at 80kts. The grey blades are a good start getting rid of the problem.