Rescue Line Pendulum Effect ?

[Jople]

 

Done… We already have Automatic Flight Control and Stability Augmentation systems in place like the automatic transition to hover and stabilization systems, in the UH-60 and HH-65 (Dolphin).

 

These systems provide automatic flight control. At the pilot's direction the system will bring the aircraft to a stable hover above a selected object. This is an important safety feature over water, at night or inclement weather.

 

We have an Unmanned K-Max project flying external loads around without any abnormal swing. Stable flight control inputs and stable hovering; notwithstanding any adverse load aerodynamics, translates into a stable external load.

 

On the commercial end, day VFR operations can normally be completed safely without any additional flight control avionics and without any unwanted swing. Training and good pilot/crew coordination is key. Pilots trained in vertical reference can also safely complete the task.

 

Well-trained pilot/crew teams and vertical reference pilots don’t seem to have much if any problems handling “Pendulum effect" or "line-swing" issues.

 

Over the years much research and wind tunnel testing has gone into this effort and the following are a few of those projects:

 

CIFER - Externally Slung Loads - Ames Research Center, Moffett Field

Flight-control - Externally Slung Loads ... Ames Research Center, Moffett Field

Rotorcraft with Externally Slung Loads ... Ames Research Center, Moffett Field

Automatic Flight Control System

 

 

Concerning technical terms in the following;

 

CIFER - Externally Slung Loads - Ames Research Center, Moffett Field

 

In the Abstract the following;

Flight test certification of helicopter-slung load

configurations can be time consuming and expensive

when quantitative evaluations of the system’s handling

qualities, stability, and envelope are required. These costs

can be significantly reduced by conducting the analysis

during the flight test using telemetry data. The analysis is

done following the completion of a test point and prior to

clearing the aircraft to the next test point. A method for

Copyright Ó 1999 by the American Institute of Aeronautics and

Astronautics, Inc. No copyright is asserted in the United States

under Title 17, U.S. Code. The U.S. Government has a royaltyfree

license to exercise all rights under the copyright claimed

herein for Governmental purposes. All other rights are reserved

by the copyright owner.

doing this which employs the CIFER® software package

for frequency domain analysis of frequency sweep data

has been demonstrated in recent slung load flight tests at

Ames Research Center. This paper describes the flighttime

computational procedure and an efficient graphical

user interface designed for the flight-time computations,

and presents flight test results. Aircraft frequency

responses, handling qualities parameters, stability

margins, and load pendulum roots were identified. These

computations required about 3 minutes on the 36 MHz

workstation used during the flight tests, and this was

reduced below 40 seconds on a more modern workstation

with 195 MHz processor. The results obtained during the

flight test are compared to results from postflight analysis

with a more accurate algorithm and with “cleaner” data

recorded onboard the aircraft. These comparisons show

that the flight-time results provide an accurate assessment

of the system dynamic characteristics.

 

 

Concerning the, (Highlighted in Red), this time is descriptive of analysis or a reference to the time it took to make the anlysis, Correct.

Reason I am asking is "why post the measurement time when what I want is the time it takes to correct the swinging.

 

I am searching for the time it takes for the pilot to correct the "Pendulum Swing", manually or using a control mechanism.

 

The following was described to me concerning manual correction.

 

Whenever a helicopter pilot has an external load that starts to swing (Human or non-human cargo), he will begin to slowly turn and the swinging will cease.

Initiating a shallow turn will remedy the pendulum effect by decreasing the ability for the load to swing by using centrifugal force. Even at a slow forward speed with a shallow turn to one direction, it will create a G Force on the weight, increasing the relative weight on the end of the rope and diminishing the swing.

The time this takes I would like to compare for analysis to what I find in the various Papers on, "Externally Slung Loads-Flight Controls"

Edited May 23, 2013 by Jople

[iChris]

 

Concerning the, (Highlighted in Red), this time is descriptive of analysis or a reference to the time it took to make the anlysis, Correct.

Reason I am asking is "why post the measurement time when what I want is the time it takes to correct the swinging.

 

I am searching for the time it takes for the pilot to correct the "Pendulum Swing", manually or using a control mechanism.

 

The following was described to me concerning manual correction.

 

Whenever a helicopter pilot has an external load that starts to swing (Human or non-human cargo), he will begin to slowly turn and the swinging will cease.

Initiating a shallow turn will remedy the pendulum effect by decreasing the ability for the load to swing by using centrifugal force. Even at a slow forward speed with a shallow turn to one direction, it will create a G Force on the weight, increasing the relative weight on the end of the rope and diminishing the swing.

The time this takes I would like to compare for analysis to what I find in the various Papers on, "Externally Slung Loads-Flight Controls"

 

They’re concerned with flight test certification of helicopter-slung load configurations and the evaluations of the helicopters handling qualities, stability, and control envelope. The time they’re talking about is the time needed to make the analysis.

 

The time it takes to correct an inadvertent swing depends on what caused it. Was it caused by out of sync or erratic control inputs by the pilot or is the load oscillating as a result of the aerodynamic forces due to the current airspeed.

 

Is the attaching line length short or long? The shorter the line the shorter the swing period and the easier it is to reorient the load under the helicopter. However, the longer lines have longer swing periods (slower load movement) and allow the pilot more time to smoothly move the helicopter back over the load in order to stop the swing.

 

That period time T is a function of the line length l and gravity g (T= 2π√l/g). This is a quick estimation using the period of a pendulum formula. You can see from the formula any increased acceleration due to gravity will decrease the swing. Suddenly lowering the collective will decrease the tension and change the dynamics and shorten the swing too. The time it would take is anyone’s guess; it depends on each pilot’s ability. Maybe six to eight periods would be a reasonable average to stop a swing.

 

Again, on the commercial end, day VFR operations can normally be completed safely without any additional flight control avionics and without any unwanted swing. Training and good pilot/crew coordination is key. Pilots trained in vertical reference can also safely complete the task. Well-trained pilot/crew teams and vertical reference pilots don’t seem to have much if any problems handling “Pendulum effect" or "line-swing" issues.

 

Period of a Pendulum Used Here As Quick Estimation Only

 

Period of a Pendulum Simulation

Edited May 26, 2013 by iChris

[Jople]

Thanks Chris, In other words, without reading any further, I assume that as you say it is up in the air concerning the, "swing effect", concerning the time and effort to correct, . . the point I am getting at , is as viewed in some commentaries showing the, "swing effect", is the time and distance, allowable, for example, when a rescue mission is involved with close quarters such as, where there are electric wires, stone walls, cliffs, fires and the like, the un-practicabilities, leave a certain risk factor. In these cases the time and distance to ,"correct", may be vital to the success of the mission. Why go on saying that it is to expensive to provide a technology, that will solve the problem, . . Although my understanding of aero- engineering and dynamics, is limited I have yet to glean that solution from the technical data, etc. However I am interested in proposing a possible solution to DOD contractors, and BS to the cost.

Edited May 26, 2013 by Jople

[iChris]

In these cases the time and distance to ,"correct", may be vital to the success of the mission. Why go on saying that it is to expensive to provide a technology, that will solve the problem, . . Although my understanding of aero- engineering and dynamics, is limited I have yet to glean that solution from the technical data, etc. However I am interested in proposing a possible solution to DOD contractors, and BS to the cost.

 

 

 

Again, well-trained pilot/crew teams and vertical reference pilots don’t seem to have much if any problems handling “Pendulum effect" or "line-swing" issues. There are no un-practicalities with regard to line-swing with these highly trained crews. These people do it from start to finish without any of this “Pendulum effect" or "line-swing" you’re talking about.

 

If an operator can’t hold the line from start to finish without unwanted swing, they can’t do this type of rescues work. They’ll have to get better or move aside and let those who can take-up the slack.

 

Unless you’re involved in longline rescues at night, in low visibility, or over water under low visibility, there’s no need for expensive hardware or new technology trying to solve an insubstantial problem for day VFR operations.

 

There’s no problem here Jople.

 

'>http://youtu.be/iHEgl0x1KzA

Edited May 27, 2013 by iChris

[Hobie]

I hope Chris is on the procurement committee.

[Jople]

If you say so, . .

 

but then again, . . That's just the point, from some information I've been exposed to some rescues don't go off at night.

 

I didn't see any wires walls or other obstructions that the mission is hampered by.

 

Let me search around for a flash flood rescue, and I know there are more, I'm a little busy but give me time, I'll spend a couple hours this week locating some, "pendulum effects" reports.

 

I'm not trying to pull off a hard or soft sell, I am just convinced with increase use of helicopter rescue, we will see or hear of more incidents.

[Spike]

I'm not trying to pull off a hard or soft sell, I am just convinced with increase use of helicopter rescue, we will see or hear of more incidents.

 

 

Possibly so, however, not due to “pendulum swing” (load oscillations). It would be from operator/pilot error….

 

Commercial sector long lining is a highly precise operation. These pilots rarely, if ever, get into trouble due to pendulum effect. The reason is; they train (in the machine) and apply that experience into their work environment, continually, and thus become precision operators.

 

 

Incorporate the commercial sector philosophy into Public Safety rescue operations and you’d see an increased safety margin…..

 

 

Edited May 30, 2013 by Spike

[Counterrotate]

If you say so, . .

 

but then again, . . That's just the point, from some information I've been exposed to some rescues don't go off at night.

 

I didn't see any wires walls or other obstructions that the mission is hampered by.

 

Let me search around for a flash flood rescue, and I know there are more, I'm a little busy but give me time, I'll spend a couple hours this week locating some, "pendulum effects" reports.

 

I'm not trying to pull off a hard or soft sell, I am just convinced with increase use of helicopter rescue, we will see or hear of more incidents.

Any operator that has been trained sufficiently in external load operations knows how to stop the pendular action of the load. It's really not that hard. If I can do it, anyone can. I'm a trained monkey. No one needs to put a complex, probably heavy, and most likely expensive piece of weight shifting gear on their aircraft. Your neat little animation there shows FAR more movement than I have ever seen or experienced. And all the pilot in that situation would need to do to stop that swing is back the helicopter away from the power lines. The lateral movement of the helicopter would stop the swing pretty quickly as well as get those on the end of the line away from the hazard. You really are trying to create a solution that common sense and pilot ability have already taken care of. Any situations where a pilot lost control of a load were almost assuredly due to poor judgement and pilot error. No mechanical device ever created has been able to compensate for pilot error. Autopilot helps though... You can go ahead and develop your device anyway if you don't believe us. Good luck selling it...

[Rupert]

Those who CAN fly a long line consider it easy. Those who have yet to figure it out consider it difficult.

 

The FAA says that helicopter pilots have a 20 year apprenticeship, and even after the 20 years, they still have accidents.

 

We now have a new generation of helicopters coming into existence, starting with the EC 145 and AW 139, that have sufficient power and sophisticated enough stability augmentation systems, that helicopter pilots no longer will require a 20 year apprenticeship.

 

In other words, manufacturers have begun to build the expertise into the helicopter instead of expecting the pilot to bring the expertise.

 

I grew up in this industry flying what now pass for antiques. The new pilots don't fly the antiques as well as do the old guys. However, the new guys can manage a cockpit very well. The new guys grew up in households that had computers and smart phones, and they learn and manage systems well.

 

Welcome to the future.

[Counterrotate]

Those who CAN fly a long line consider it easy. Those who have yet to figure it out consider it difficult.

 

The FAA says that helicopter pilots have a 20 year apprenticeship, and even after the 20 years, they still have accidents.

 

We now have a new generation of helicopters coming into existence, starting with the EC 145 and AW 139, that have sufficient power and sophisticated enough stability augmentation systems, that helicopter pilots no longer will require a 20 year apprenticeship.

 

In other words, manufacturers have begun to build the expertise into the helicopter instead of expecting the pilot to bring the expertise.

 

I grew up in this industry flying what now pass for antiques. The new pilots don't fly the antiques as well as do the old guys. However, the new guys can manage a cockpit very well. The new guys grew up in households that had computers and smart phones, and they learn and manage systems well.

 

Welcome to the future.

I have not seen ANY sign or trend indicating that less hours or expertise will be required to fill those seats. The tech on the horizon that I am seeing is all going into passenger transport role aircraft. We are seeing more and more corporate sector and offshore helicopters that are getting bigger, faster, and easier for the pilot to fly and navigate. Basically, the point a to point b type flying is where we are seeing all the glass and autopilots. In the utility sector, it is still all Hueys and MDs and Astars with the guts ripped out of them to save weight and only enough instrumentation to get the job done safely. There is no substitute for experience in this industry and that is simply not going to change any time soon.