Vuichard Recovery

[Hand_Grenade_Pilot]

This maneuver has been around for awhile, but I have not had the opportunity to practice or experiment with it. My understanding is that to recover from VRS (with a counter-clockwise MR) you can apply max available power, right cyclic and left pedal to laterally transition into a clean airflow. The application of left pedal assists in creating lateral movement (translating tendency) to expedite the transition out of VRS.

 

The demonstrations seem very effective. However, in talking with other pilots, there has been a lot of disagreement regarding the application, effectiveness and stress induced on the aircraft. So Id like to open a discussion to the community to discuss a few key points.

 

1.) What is your opinion regarding the Vuichard Recovery?

2.) Does your company / department / flight school practice the maneuver?

3.) Is the maneuver only effective to the right (counter-clockwise MR)? If one were to use left cyclic, would counteracting translating tendency compromise the maneuver?

4.) Is there any evidence that the maneuver imposes significant stress on the aircraft? If so, which components?

5.) Is teaching this maneuver worth the risk of being performed incorrectly? For instance, a pilot accustomed to performing a traditional VRS recovery (forward or lateral cyclic, slight reduction in collective) accidentally combining control inputs between the old and new technique (such as raising collective while applying forward cyclic).

 

For reference, here are some links on the Vuichard Recovery:

 

http://www.ihst.org/portals/54/airmanship/Airmanship%20Vuichard%20FINAL.pdf

 

https://m.youtube.com/watch?v=HjeRSDsy-nE

[r22butters]

First time I did this new technique was at the Robinson Safety Course. Its pretty easy to do, and kinda cool.

 

However when I got myself into real settling with power one day, Its funny that my first though was, "how does that new technique go again?" Then I just said f*ckit and pushed forward.

 

I think it may be hard for us old guys who learned exclusively on the old way, but maybe these new kids will have it as a built in reflex?

 

,...though on my last BFR I asked the instructor if he wanted to do the new technique and he said he wasn't all that familiar with it yet, so,...?

 

Oh yeah, to answer at least one of your questions, I was asked to perform the new technique during a job interview. So although the school I rent from doesn't seem to be all in at the moment, I know at least one tour company who does embrace it.

Edited June 2, 2019 by r22butters

[iChris]

This maneuver has been around for awhile, but I have not had the opportunity to practice or experiment with it. My understanding is that to recover from VRS (with a counter-clockwise MR) you can apply max available power, right cyclic and left pedal to laterally transition into a clean airflow. The application of left pedal assists in creating lateral movement (translating tendency) to expedite the transition out of VRS.

 

The demonstrations seem very effective. However, in talking with other pilots, there has been a lot of disagreement regarding the application, effectiveness and stress induced on the aircraft. So Id like to open a discussion to the community to discuss a few key points.

 

1.) What is your opinion regarding the Vuichard Recovery?

 

The maneuver they are now calling the Vuichard Recovery, is an informal facelift of a maneuver that has been around for a long time.

 

It was known long ago in technical circles, that any forward, lateral, or edge-wise movement of the rotor would aid in the recovery from VRS. For the single rotor helicopter, it was commonly understood that forward cyclic and reduce collective was the easiest to accomplish; therefore, it became the norm. For the tandem rotor lateral movement became the norm. In general context, the technique is valid under certain circumstances.

 

Another area of concern, pilots sometimes have difficulty recognizing the difference between VRS state and settling with power, much less which technique to use under each of those circumstances.

 

The claims maybe a bit exaggerated due to the way the data was taken and the instrumentation used to take the data. Moreover, it’s very difficult to determine the exact position of the aircraft with respect to the area of severe turbulence, as a result the aircraft ends up in the light turbulence area (the early stages of vortex ring state). As a consequence, the data doesn’t reflect the severe turbulence encountered in a fully developed vortex ring state. This may not be the silver bullet, magic bullet, foolproof, or fix-all as advertised.

 

A more critical examination of the techniques overall capability and suitability needs to be accomplished. Moreover, independent flight test and engineering data compiled, analyzed, and published.

 

We’ve posted on this recovery issue, See the link below:

 

The Vuichard Recovery - Flying Through the Vortex

Edited June 2, 2019 by iChris

[Wally]

I tried the Vuichard at a recurrent training session a few years ago with an instructor who also did utility in the Rockies. We had, of course, done the FAA approved syllabus maneuvers...

The instructor took the time to demonstrate it and allowed me to execute a few, maybe several times (it was a pretty intense training session, and I learned a lot). I am confident that we were in a developed VRS at each attempt, but as iChris points out, it's hard to repeat specific states and establish real, demonstrable advantages.

For transparency, I HATE the approved recovery technique. Perhaps a carryover phobia from teaching it in TH-55s? Continuing the descent as one reduces power and noses down to fly out feels like trying to time the bullet that one accidently fired at your forehead.

The Vuichard seemed a more positive, quicker recovery with less altitude loss. It didn't seem to matter which pedal and I didn't feel anything unusual in aircraft response.

 

AWARENESS! AWARENESS! AWARENESS! A real appreciation of the potential VRS, a plan to deal with the issue and/or abort whatever operation you're attempting. The VRS situation is predictable, controllable if one doesn't get distracted. I never had a real life VRS, but I became a devout and faithful believer in S-L-O-W approaches with minimal control inputs, especially power changes until the skids are down- just as PHI taught in'83. Everything after the turn to final should be imperceptible changes.

[iChris]

This maneuver has been around for awhile, but I have not had the opportunity to practice or experiment with it. My understanding is that to recover from VRS (with a counter-clockwise MR) you can apply max available power, right cyclic and left pedal to laterally transition into a clean airflow. The application of left pedal assists in creating lateral movement (translating tendency) to expedite the transition out of VRS.

 

The demonstrations seem very effective. However, in talking with other pilots, there has been a lot of disagreement regarding the application, effectiveness and stress induced on the aircraft. So Id like to open a discussion to the community to discuss a few key points.

 

 

3.) Is the maneuver only effective to the right (counter-clockwise MR)? If one were to use left cyclic, would counteracting translating tendency compromise the maneuver?

 

5.) Is teaching this maneuver worth the risk of being performed incorrectly? For instance, a pilot accustomed to performing a traditional VRS recovery (forward or lateral cyclic, slight reduction in collective) accidentally combining control inputs between the old and new technique (such as raising collective while applying forward cyclic).

 

Again, the Vuichard Recovery is an informal facelift of flight dynamics that were documented years ago. Any forward, lateral, or edge-wise movement of the rotor will aid in the recovery from VRS. In fact, used that combination in your post, raising collective while applying forward cyclic, it’s an applicable recovery technique.

 

Remember, the Vuichard technique assumes the helicopter’s rotors are engulfed in VRS. The majority of the time that’s not the case and any pilot making that assumption may be in for a rude awakening. Most of these reported VRS encounters are the old, backside of the power curve, power-available less than power-required, so-called settling accidents. Similar conditions, high rate of descent with respect to power and airspeed, but less than required for VRS.

 

The pilot makes the wrong assumption, it’s a power available problem, not VRS. The old technique, slight-lowering of the collective and forward cyclic, aids in the recovery in either situation, the Vuichard techniques requires more of what the pilot doesn’t have, excess power. The resulting request for power where there is not enough power comes at the cost of a reduction in rotor RPM and an increase in descent rate.

 

We have individuals running about promoting this like it’s a new discovery. Safety awards being handed out, magazine articles, seeking addition into the ASA Helicopter Flying Handbook. One of the individuals promoting this is the fellow, some years back, that started teaching and demonstrating recovery techniques to CFIs in the Robinson regarding low-G and low-G pushovers and the resulting right-roll, by actually introducing a pushover to affect a right-roll, then demonstrating how to recover and avoid the mast dumping. That’s playing with dynamite. Fortunately, it was discontinued.

 

Don’t be gullible, sometimes you have to follow-up on the individual egos involved and money trail to get to the bottom of what’s really promoting all of this. It’s definitely not a new discovery nor were any of these techniques developed by Vuichard.

 

Below are some of the things we’ve learned from technically skilled individuals in our industry like Raymond W. Prouty, Dr. J. Gordon Leishman, and Nick Lappos:

 

Any forward, lateral, or edge-wise movement of the rotor would aid in the recovery from VRS.

 

Increasing the collective does not necessarily aggravate the VRS, however, increasing collective was an uncertain way to quickly leave VRS, then again, an increased forward velocity stabilized the rate of descent.

 

Flight in vortex ring state is unpredictable. Two VRS flights starting from close conditions could imply very different helicopter reactions. This chaotic behavior is probably explained by the turbulent flow producing VRS.

 

In a hover, you cannot get VRS until the aircraft has an appreciable rate of descent, usually beyond 700 feet per minute, likely about 1200 fpm or more.

 

For VRS to occur, the upward component of velocity normal to the rotor disk plane must be a substantial fraction of the average induced velocity downward through the rotor disk. Our knowledge of the VRS comes from flight and wind tunnel tests. Based on this experience, we know that unsteadiness starts between .25 - 0.5, peaks at .75 – 1.0, and disappears at 1.5 times the hover induced velocity.

 

The strongest unsteady VRS conditions can be obtained at high rates of descent but with some small forward speed (i.e. a small edgewise component of the induced velocity parallel to the disk).”

 

During the initial stage (when a large amount of excess power is available), a large application of collective pitch may arrest rapid descent. If done carelessly or too late, a collective increase can aggravate the situation resulting in more turbulence and an increased rate of descent.

 

In a wind tunnel or long track test, the instability can be documented because the model can’t go anywhere. In flight, however, the instability prevents the pilot from finding a steady flight condition in which to take data. The flight test points in the literature that are identified as being taken in the vortex ring state were undoubtedly obtained under highly transient conditions.”

 

“Pilots use two terms, “settling with power” and “power settling”—sometimes interchangeably and sometimes to represent two different situations. One is the vortex ring condition discussed above. The other is simply entering into a flight condition where the required power is more than the available power.

 

“Staying in the vortex ring for any length of time isn’t easy. It depends upon maintaining a nearly vertical flight path. There is some evidence, however, that a “glide” slope of about 70° is worse than a true 90° descent.”

 

“Theoretically, the vortex-ring state exists from hover until the rate of descent is high enough to put the rotor onto the lower windmill-brake branch. But from a practical standpoint, the extreme flow variations do not start until the rate of descent is about half the hover induced velocity and they taper off before vertical autorotation is reached.”

Edited June 14, 2019 by iChris