Confined Areas

[Phil Croucher]

Some really good material there which I will be working on. Thanks!

 

The other thing that will be included in the proposed syllabus, though I don't think there will be any questions, is the wearing of helmets. And the private operator stuff is going to be removed from air law.

 

Looks like a common-sense regime in there right now.

 

phil

[deltacharlie]

This sounds a little like "The Spinning Takeoff." Ken Armstrong wrote about it in his safety article the April/May/June 2004 Helicopters Magazine. It's the last paragraph. HERE.

 

And when it goes bad.. Video.

 

What the HE** was that? He wasn't even near confined...something else went wrong there.

 

DC

[Helilog56]

Looks like a classic example of LTE....

[Jet B]

What the HE** was that? He wasn't even near confined...something else went wrong there.

 

DC

 

 

Yeah, that video was pretty much insane...

 

[Helilog56]

While we are on the subject.....some reminders for us all, from my notes I collected over the years.

 

Four aircraft characteristics during low speed flight have been identified through extensive flight and wind tunnel tests as contributing factors in unanticipated right yaw.

 

For the occurrence, certain relative wind velocities and azimuths (direction of relative wind) must be present. The aircraft characteristics and relative wind azimuth regions are:

 

Weathercock stability (120 to 240 degrees)

Tail rotor vortex ring state (210 to 330 degrees)

Main rotor disc vortex interference (285 to 315 degrees)

Loss of translational lift (all azimuths)

The aircraft can be operated safely in the above relative wind regions if proper attention is given to controlling the aircraft. However, if the pilot is inattentive for some reason and a right yaw rate is initiated in one of the above relative wind regions, the yaw rate may increase unless suitable corrective action is taken.

 

WEATHERCOCK STABILITY (120 to 240 DEGREES)

Winds within this region will attempt to weathervane the nose of the aircraft into the relative wind. This characteristic comes from the fuselage and vertical fin. The helicopter will make an uncommanded turn either to the right or left depending upon the exact wind direction unless a resisting pedal input is made. If a yaw rate has been established in either direction, it will be accelerated in the same direction when the relative winds enter the 120 to 240 degree area, unless corrective pedal action is made. The importance of timely corrective action by the pilot to prevent high yaw rates for occurring cannot be overstressed.

 

TAIL ROTOR VORTEX RING STATE (210 to 330 DEGREES)

Winds within this region, will result in the development of the vortex ring state of the tail rotor. The vortex ring state causes tail rotor thrust variations which result in yaw rates. Since these tail rotor thrust variations do not have a specific period, the pilot must make corrective pedal inputs and the changes in yaw acceleration are recognized. The resulting high pedal workload in tail rotor vortex ring state is well known and helicopters are operated routinely in the region. This characteristic presents no significant problem unless corrective action is not timely. If a right yaw rate is allowed to build, the helicopter can rotate into the wind azimuth region where weathercock stability will then accelerate the right turn rate. Pilot workload during vortex ring state will be high; therefore, the pilot must concentrate fully on flying the aircraft and not allow a right yaw rate to build.

 

TAIL ROTOR VORTEX RING STATE (210 to 330 DEGREES)

Winds within this region, will result in the development of the vortex ring state of the tail rotor. The vortex ring state causes tail rotor thrust variations which result in yaw rates. Since these tail rotor thrust variations do not have a specific period, the pilot must make corrective pedal inputs and the changes in yaw acceleration are recognized. The resulting high pedal workload in tail rotor vortex ring state is well known and helicopters are operated routinely in the region. This characteristic presents no significant problem unless corrective action is not timely. If a right yaw rate is allowed to build, the helicopter can rotate into the wind azimuth region where weathercock stability will then accelerate the right turn rate. Pilot workload during vortex ring state will be high; therefore, the pilot must concentrate fully on flying the aircraft and not allow a right yaw rate to build.

The loss of translational lift results in increased power demand and additional anti-torque requirements. If the loss of translational life occurs when the aircraft is experiencing a right turn rate, the right turn will be accelerated as power is increased, unless corrective action is taken by the pilot. When operating at or near maximum power, this increased power demand could result in rotor rpm decay.

 

The characteristic is most significant when operating at or near maximum power and is associated with unanticipated right yaw for two reasons. First, if the pilot's attention is diverted as a result of an increasing right yaw rate, he may not recognize that he is losing relative wind and hence losing translational lift. Second, if the pilot does not maintain airspeed while making a right downwind turn the aircraft can experience an increasing right yaw rate as the power demand increases and the aircraft develops a sink rate. Insufficient pilot attention to wind direction and velocity can lead to an unexpected loss of translational lift. The pilot must continually consider aircraft heading, ground track, and apparent groundspeed, all of which contribute to wind drift and airspeed sensations. Allowing the helicopter to drift over the ground with the wind results in a loss of relative wind speed and a corresponding decrease in the translational lift produced by the wind. Any reduction in translational lift will result in an increase in power demand and anti-torque requirements.

 

 

RECOVERY TECHNIQUE

If a sudden unanticipated right yaw occurs, the following recovery technique should be performed:

 

Pedal - full left; simultaneously, cyclic - forward to increase speed.

As recovery is effected adjust controls for normal forward flight.

 

CAUTION

COLLECTIVE PITCH REDUCTION WILL AID IN ARRESTING THE YAW RATE BUT MAY CAUSE AN EXCESSIVE RATE OF DESCENT. THE SUBSEQUENT LARGE, RAPID INCREASE IN COLLECTIVE, TO PREVENT GROUND OR OBSTACLE CONTACT, MAY FURTHER INCREASE THE YAW RATE AND DECREASE ROTOR RPM.

 

THE DECISION TO REDUCE COLLECTIVE MUST BE BASED ON THE PILOT'S ASSESSMENT OF THE ALTITUDE AVAILABLE FOR RECOVERY.

 

 

If spin cannot be stopped and ground contact is imminent, an autorotation may be the best course of action. Maintain full left pedal until the spin stops, then adjust to maintain heading.

Note

 

The various wind directions can cause significantly differing rates of turn for a given pedal position. The most important principle for the pilot to remember is that THE TAIL ROTOR IS NOT STALLED. Thus, the corrective pedal position to be applied is always in the normal direction of OPPOSITE PEDAL to the turn direction.

[Helilog56]

Let me try to explain where I'm coming from in the previous described,"release pedal" technique. I was not being so critical....but to get us to think of potential repercussions !

 

I have also spent many years (like others here), as a working pilot (still do), a C.P., a C.P.P., and flight instructor and training captain (SK64).

What I am elaborating on, is from my personal experience and observations.

 

By reading my prior post, it comes to light, that as pilots we have only a certain amount of control over our environment.....what I mean particularly is winds.

 

Particularly, how those winds affect rotor wash (vortices). I am sure you all have had mild, moderate, and severe tail kicks while flying.......especially at high power settings below translational lift........ever think about the strain put on the airframe????

The bigger the ship.....the more severe the strain.

 

But this is about maintaing good aircraft control (airmanship), especially "yaw", and not adding unecessary workload or risk.

 

I have observed and tried, the release the pedal at high power settings.......and "yes", on "occasion", it can work. "But".....if the rate of turn starts to accelerate, the first reaction for the pilot is to arrest that with opposite pedal, if it is a counerclockwise rotating main rotor and you use left pedal what do you think happens to the torque if you are at "max" ????

 

Add high D.A, decaying rotor rpm, trying to achieve airspeed to quickly, and you have a recipe for disaster.

 

My preferrence (for myself) is to always have a "loaded" t/r (especially below translational), which helps give excellent yaw/heading control. That, and a good power assesment, to "know", that before I commit to a departure, which may be a "standard", "cushion (low power)", or a "vertical" takeoff.

 

Good "basic" handling techniques are where its at......... Good flight manual knowledge, a power assesment, load the disc, load the t/r, hold your ground position (patience), smooth light acceleration (without spilling lift), "quiet" cyclic, wind direction and strenght (or lack of it), maintaining an "escape route" if someting goes wrong........these are the real "tricks", to safe flying !!!!????

 

Safe flying!

[Guest Up&away]

I have never tried your methods and never will. It leaves nothing in the bank if you screw up which letting the aircraft rotate right (on a bell) to allow you to get out of hole instead of kicking out some weight is a accident waiting to happen. Look at your flight manual charts how many feet to get over a 50 ft obstacle. Your outside the performance of the aircraft. I never turn right to get out of a hole I always go left and make sure I have enough power so I can return to my spot if something does not go right. As far as you need these procedures to survive in the mountains or stay home is bull. I survive the mountains this way and have no problems.

[Black Mike]

I have never tried your methods and never will. It leaves nothing in the bank if you screw up which letting the aircraft rotate right (on a bell) to allow you to get out of hole instead of kicking out some weight is a accident waiting to happen. Look at your flight manual charts how many feet to get over a 50 ft obstacle. Your outside the performance of the aircraft. I never turn right to get out of a hole I always go left and make sure I have enough power so I can return to my spot if something does not go right. As far as you need these procedures to survive in the mountains or stay home is bull. I survive the mountains this way and have no problems.

 

U and A,

 

If you don't like this method, don't do it. It was not something I do everyday, just a procedure that might be helpful sometime. It saved myself from an overtorque inspection during fire season 2003 where, had I done 2 trips out of the confined area, the second trip would have been with a crew person in a body bag. Not planned, it just happened that I was the closest machine to do the rescue.

 

As for the mountains, whatever works for you is the way to go. My methods have kept me safe in the past 34 years that I have been flying in the Coast Range.

 

By the way, I didn't invent these little tricks that we use in the mountains, I just hear about them, try them out, and do what feels the best for the conditions. This tail rotor trick only works in certain conditions, and if these are not obvious to you, guaranteed you will get into trouble.

 

If you don't agree, this is fine- just go on to the next post.

 

Phil, sorry if I tied up your thread, I will sign off until January. Have a great holiday season.

 

B.M.

 

 

 

 

[Phil Croucher]

Thanks for your input, Mike! I am in the Logic Free Zone (UAE) until mid Jan, cooking up the text to go with all your comments.

 

My best wishes to all of you for the non-PC Christmas and New Year hols. Or if you're a pagan the festival of the Return Of the Sun.

 

Phil

[C-FXFX]

I have never tried your methods and never will. It leaves nothing in the bank if you screw up which letting the aircraft rotate right (on a bell) to allow you to get out of hole instead of kicking out some weight is a accident waiting to happen. Look at your flight manual charts how many feet to get over a 50 ft obstacle. Your outside the performance of the aircraft. I never turn right to get out of a hole I always go left and make sure I have enough power so I can return to my spot if something does not go right. As far as you need these procedures to survive in the mountains or stay home is bull. I survive the mountains this way and have no problems.

 

 

Your correct when you say ¨YOU LEAVES NOTHING IN THE BANK!¨but read all post

 

No one say it is a ¨Tout les jours!¨ normal operation! but it can be helpfull to do it and if you do it do it right! IT CAN SAVE YOUR ***!!!!

 

That's what B.M.....k say in 82 in YFC when i was doing my training he show me the DO and DON'T in different situation and it is why i can still write this post today!

 

By the way BM you description of the procedure is so true i'm still hearing Brian discribe in the intercom it many moon ago!

 

Best time of my life!

 

Guy