8083-21 omissions & errors

[Mikemv]

In a USHST workshop on Friday (8-23-2013), I was having a discussion with a DPE that has given 8,000+ helicopter practical test. He pointed out that the HFH, FAA-H-8083-21A has some errors in the paragraph below:

 

 

Low-G Conditions and Mast Bumping pg 11-14

Low acceleration of gravity (low-G or weightless) maneuvers create specific hazards for helicopters, especially those with semirigid main rotor systems because helicopters are primarily designed to be suspended from the main rotor in normal flight with only small variations for positive G load maneuvers. Since a helicopter low-G maneuver departs from normal flight conditions, it may allow the airframe to exceed the manufacturer’s design criteria. A low-G condition could have disastrous results, the best way to prevent it from happening is to avoid the conditions in which it might occur.

Low-G conditions are not about the loss of thrust, rather the imbalance of forces. Helicopters are mostly designed to have weight (gravity pulling down to the earth) and lift opposing that force of gravity. Low-G maneuvers occur when this balance is disturbed. An example of this would be placing the helicopter into a very steep dive. At the moment of pushover, the lift and thrust of the rotor is forward, whereas gravity is now vertical or straight down. Since the lift vector is no longer vertical and opposing the gravity (or weight) vector, the fuselage is now affected by the tail rotor thrust below the plane of the main rotor. This tail rotor thrust moment tends to make the helicopter fuselage tilt to the left. Pilots then apply right cyclic inputs to try to correct for the left. Since the main rotor system does not fully support the fuselage at this point, the fuselage continues to roll and the pilot applies more right cyclic until the rotor system strikes the mast (mast bumping), often ending with unnecessary fatal results. In mast bumping, the rotor blade exceeds its flapping limits, causing the main rotor hub to “bump” into the rotor shaft.

The Low G info is correct in the HIH, chap 12, pgs. 12-8, 12-9.

CFI's please address this with your pilots in training.

I pointed out that in chapter 9, the "vertical landing from a hover" is missing.

We were working on PTS changes for CFI, Comm. & Private and also formed a sub-committe to work on the Integrated Airman Certification Standards (IACS) that hopefully will be published by FAA FY17 for rotorcraft-helicopters.

All of this is about accident reduction and best practices flight & ground training.

Sorry, AS POINTED OUT BELOW, I left the "A" off of the 8083-21A and this copy & paste is from the 21A.

Mike

Edited August 25, 2013 by Mikemv

[WolftalonID]

Something to consider is the publication reference. I have that book as the 2000 edition. Its information is page 11-10 and is correct for robinson helicopters.

 

The current publication FAA-H-8083-21 id specified as for gyroplanes only, hence the information is somewhat different.

The FAA has designated a new publication separating helicopters from gyroplanes. It is FAA-S-8083-21A.

Have you compared your publication with the FAA to verify you have to current helicopter edition? Also note, the older 2000 edition where both gyro and helicopters are combined does have it printed correctly for robinson helicopters.

 

One last note is, low G roll is relative to tail rotor thrust direction. Typically trainer helicopters have counter clockwise rotating rotor, and the tail rotor causes an in air dynamic roll effect to the right. However, clockwise rotational rotors have tail rotor thrust opposite, thus a left roll could occur.

[Mikemv]

WolftalonID,

 

My info is from the current HFH 21A. As you stated, -21 was the now dated RFH.

 

I went back and corrected it above!

 

Gyros are now in a new -35

 

Mike

Edited August 25, 2013 by Mikemv

[Mikemv]

WolftalonID,

 

You stated "One last note is, low G roll is relative to tail rotor thrust direction. Typically trainer helicopters have counter clockwise rotating rotor, and the tail rotor causes an in air dynamic roll effect to the right. However, clockwise rotational rotors have tail rotor thrust opposite, thus a left roll could occur."

 

 

And which semi rigid training or other helicopters would be turning clockwise?

 

Mike

[WolftalonID]

Low G conditions and Mast bumping are two seperate things. In semi rigid rotor systems low g is dangerous as to creating a condition leading to mast bumping.

 

However, go low G in just about any helicopter, and the tail rotor can cause the low g roll effect, minus the mast bumping reserved for semi ridgid, two blade systems. Controlling forces in articulated blade systems tend to stay positive, and mask the full effect of the roll.

 

Those that fly the AS350 can possibly speak up more on the extent of low g in the clockwise fully articulated systems. They obviously are not going to lead into mast bumping as would a teetering hub, but that is not the same as the dynamic roll from the couple made from the tail rotor leverage and its relation to the fusalage of the aircraft in low g flight.

 

I have one question from the OP. the line highlighted in red about it NOT being from a loss of thrust. Are you saying that thrust IS gone? The rotor is still producing thrust even when the fuselage is not pulling against it, that thrust is still being vectored via hard line controls.

The helicopter is just not the weighted pendulum following the blades, now its free floating or possibly pushing into the blades coning angles.

[Mikemv]

"I have one question from the OP. the line highlighted in red about it NOT being from a loss of thrust. Are you saying that thrust IS gone? The rotor is still producing thrust even when the fuselage is not pulling against it, that thrust is still being vectored via hard line controls."

 

It was the DPE that pointed out the areas in red being incorrect as I stated in the OP.

 

loss-gain, increase-decrease does not state "gone" in totality.

 

Thanks for your posts above as this will get pilots in training and CFIs to address/recognize the issues.

 

Mike

[WolftalonID]

I did not see that in the OP, sorry I missed it. However, its a good reason I kept my book, as new students are getting the updated editions. I will pass that on to my chief pilot as well. Thanks for posting it up!

[eagle5]

Just checked my old RFH with my new HFH and well, all I can do is reafirm the old saying,...if it ain't broke, don't fix it!

[iChris]

WolftalonID, on 25 Aug 2013 - 16:34, said:

 

Low G conditions and Mast bumping are two seperate things. In semi rigid rotor systems low g is dangerous as to creating a condition leading to mast bumping.

 

However, go low G in just about any helicopter, and the tail rotor can cause the low g roll effect, minus the mast bumping reserved for semi ridgid, two blade systems. Controlling forces in articulated blade systems tend to stay positive, and mask the full effect of the roll.

 

 

I have one question from the OP. the line highlighted in red about it NOT being from a loss of thrust. Are you saying that thrust IS gone? The rotor is still producing thrust even when the fuselage is not pulling against it, that thrust is still being vectored via hard line controls.

 

The helicopter is just not the weighted pendulum following the blades, now its free floating or possibly pushing into the blades coning angles.

 

In any steady state flight condition thrust equals weight. In a pure zero-g flight state rotor thrust is reduced to zero. In most standard teetering rotor systems control-in-roll and damping-in-roll are byproducts of rotor thrust; therefore, zero-g means a loss of control-in-roll and damping-in-roll.

 

Low-G/Zero-G conditions are about the reduction or loss of thrust that could lead to the pilot making an abrupt control input, in an effort to correct an un-commanded right roll, caused by the tail rotor thrust and in some cases main rotor torque acting about the CG.

 

In a fully articulated rotor system, control-in-roll and damping-in-roll are maintained without developing thrust. The blades of the fully articulated rotor system are attached to the rotor hub at some distance from the mast. That offset hinging allows centrifugal forces to produce control moments about the CG, independent of thrust. The additional development of thrust therefore increases the overall magnitude of the control moment, i.e, control-in-roll

Edited August 27, 2013 by iChris

[amphibpilot]

Re: corrections to FAA-H-8083-21A Helicopter Flying Handbook ("HFH")

 

There is an official HFH Errata Sheet, last updated 11 July 2013, online at:

http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/

 

Similarly, there is also an official

-Instrument Flying Handbook Errata Sheet (7/25/2013)

-Pilot's Handbook of Aeronautical Knowledge Errata Sheet (6/26/2013)

-Risk Management Handbook Errata Sheet (1/25/2013)

 

That said, unfortunately none of the actual Handbooks inform the user of the possibility of such corrections, much less their whereabouts.

 

"User beware", apparently.

Edited August 27, 2013 by amphibpilot

[eagle5]

Re: corrections to FAA-H-8083-21A Helicopter Flying Handbook ("HFH")

 

There is an official HFH Errata Sheet, last updated 11 July 2013, online at:

http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/

 

Similarly, there is also an official

-Instrument Flying Handbook Errata Sheet (7/25/2013)

-Pilot's Handbook of Aernautical Knowledge Errata Sheet (6/26/2013)

-Rish Management Handbook Errata Sheet (1/25/2013)

 

That said, unfortuneately none of the actual Handbooks inform the user of the possiblity of such corrections, much less their whereabouts.

 

"User beware", apparently.

 

 

Hmmm, did the old Rotorcraft Flying Handbook have an errata sheet (I didn't see one at the link)? I can't help but wonder what I learned to be true that was actually a typo!,...maybe the world really is flat?