Rigging Kit

[jeffhuey1n]

Some time ago, during a conversation, special tools was briefly brought up. I have a eclectic collection of tools, tool sets, tool kits, PMEL, etc. I would like to show one of my tool kits. It was an EBay purchase of a DRMO’ed tool kit. I think it’s important to have some documentation (DRMO turn in/out forms) to keep the powers that be calm. This kit was used to “rig” the flight controls of a helicopter. I seriously doubt that the kit will ever be used again. Civilian ownership of CH-53’s is extremely difficult due to the cost per flight hour, which was about $5000.00 last time I checked. I used a similar kit on the helicopters I crewed.

 

[m715mike]

Sir, what do you mean by, “rig the flight controls of a helicopter”?

 

[jeffhuey1n]

Rigging, in simple terms, means adjusting for proper dimensions. Starting in the cockpit with the “sticks” and all along the length of the flight controls, there are adjustable links. In order to make sure that any maintenance on the flight controls is done correctly, you measure each component and compare that measurement to a proper length as indicated in the technical orders. The rigging kit is installed at certain specific points.
There are pins and blocks used to ensure proper length without having to measure with a ruler, which is a royal pain. If the pins fit correctly, your job is done. If any pin or block doesn’t fit correctly, you have to make adjustments which is what we call “rigging”.

Hopefully I haven’t lost you. I worked multiple types of helicopters and each type had a rigging kit designed by the helicopter manufacturer. On the UH-1, there one item in the rigging kit. On the H-53, there are 24 +/- pins and blocks. Regardless of the type, every time maintenance is performed on anything related to the flight controls, you must check rigging.

To fully understand the process, helicopter mechanics attend schools based on the helicopter to be maintained. My first helicopter was the Marine Corps CH-53A and D. That was a six week course followed by another course that was four weeks long. That’s just to learn the basics. Once you make it to your duty station, you get more training, OJT also known as On the Job Training. I’d guess over 25 years of maintenance, I easily spent well over a year in training on all the systems and airframes of helicopters I worked on.
I hope I didn’t confuse you. I’ll be glad to try and answer any questions. I’ll poke around and see if I still have course materials.

 

[m715mike]

@jeffhuey1n that was a well written response and makes perfect sense. Thank you! I just learned something new!

 

[charlesmann]

dang, that is cheap per op hr on a 53. our 47Ds i think are billed out around $8,000/hr
yes, rigging is a nightmare at times, but i got good at it on the 47s. 60s though, nope, have no inclination to rig a 60 again. at least we don't have to rig the ECLs to our engines, compared to the 53s. but the crayon eater i was talking to the other day before he went off shift said it was hard, just could time consuming, depending how hard the person manipulating the throttles was on the levers

 

[charlesmann]

Sir, what do you mean by, “rig the flight controls of a helicopter”?

and its not just helicopters. fixed wings also have to be rigged. but rigging is even messed with on these military truck we own. similar concept, but the manuals call it "adjust turn buckle/connecting rod" to the, lets say, crane pto lever for the wreckers. or the clutch to adjust it, but anything with a manual linkage from point a to b via c, d, e, and so on, using cables or push/pull/turn buckle to bell cranks (redirection levers). ill take a pic of our flt control closet for a visual of what is being talked about

 

[charlesmann]

Cyclic, aka stick (center of pic) used for forward, backward and sideways flight, yaw pedals (foreground of pic), below the dash, used to point the nose left or right and the thrust (lower left) used for up/down, receive manual input which is transferred to the flt closet ,



where metal tubes (horizontal and vertical yellow and 1 black) with adjustable rod ends (kinda like tierod ends in the steering at the axle) meet the bellcranks (yellow thing at the bottom of the pic where the 3 ylw and 1 bl

In addition to the bellcranks mid pic with holes showing, where the pallet rig pins go through, as is the lower closet bellcranks pic below


From there, manual input has been converted to mechanical leverage/input, goes up to a 2 section hyc actuator ( back side of 2 of the 4 dual section actuator pic below) turn mech input to hyd input at the bottom, converting back to mech out/input at the top. The actuator allow the pilots to manipulate 6 375# blade, spinning 224 rpms, causing directional flight



After the above pic actuators, input is sent to the 1st and 2nd mixing, where they take 4 different axis inputs, mix them into 2 outputs, for the fwd, tunnel and aft pylon mech controls, that are connected to hyd actuators in the fwd pylon and 2 in the aft pylon, that is connected to the swashplate, which again turns hyd output back to mech input to, what looks like 3 long turnbuckles, or pc (pitch change) links that are connected to the spinning head, where the rotor blades are attached, and push/pull on a certain part of the head, causing a vertical twisting action that lifts or lowers the front of the blade, diverting airflow (like sticking your hand out the car window horizontally, while driving 60 mph, are twisting you arm causing you hand to dip or raise, which causes your arm to to follow suit).
At every connection point along the way, from cockpit to pc links, there is an adjustment that is set to X to X measurement bring the controls to a predetermined “neutral” position, providing X distance of travel.

 

[m715mike]

Wow!

How often must one rig the flight controls? I’m sure the answer depends on flight time, but was there a general rule of thumb (monthly, annually, etc.)?

How long does it take a skilled mechanic to do the rigging?

 

[charlesmann]

Wow!

How often must one rig the flight controls? I’m sure the answer depends on flight time, but was there a general rule of thumb (monthly, annually, etc.)?

How long does it take a skilled mechanic to do the rigging?

in the military, for some reason, every 400 hrs, the rig was out if certain people did the rig prior to it coming in for heavy maintenance.
it took us 30 hrs one time to get a 47d in rig bc the 2nd stage mixing was out and had to disassemble the mixing unit, which was a PIA. we burned 100 gal of jet and put 30 hrs on the apu (single stage compressor miniature gas turbine of the main engines). but in the civi side, operating the d models, we set the rig 1 time in 1200 hrs and it was out a half a turn here, half a turn there on the rod ends.
BUT, the tm says, any time a flt control component (lower actuator as pictured, or the upper actuators, control tube, definitely any rod end on a tube) is replaced, a rig verification must be done on the zone the component is in and the preceding zones.

our chinooks have 4 zones, 1. cockpit, 2. closet, 3. tunnel and 4. upper controls (fwd or aft pylon below the swashplate). if an upper actuator is replaced, a verification must be done of zone 1-4. if in the peddle box (cockpit) only zone 1. for the pc links, though, those are above the controls, and they have their own rig procedure and only gets adjusted if bearing (which have tolerance of 0.010" or less of of slop/play), meaning if its 8 thou upon inspection at a 200 hr maint interval, let it fly but be prepared to replace the bearing and have the links mag particle inspected for cracks at the next 200 hr interval or the link itself is replaced. but a test flight must be performed to adjust a pc link after its set nominal. an out of rig pc link will cause the affected blade to fly higher or lower than the corresponding blade of the affected rotor head. in addition to rigging the pc links, if a blade is replaced, adjustments of the link, along with weight adjustment in the blade must made, to again, keep the blade/s flying the same flight path with each other. and usually, that meant adjustments to other blades/links on the opposite head.

 

[Tinstar]

Basic paragraphs and readability are always appreciated.
Your post was like one continuous sentence and very difficult to read and follow due to lack of capitalization and paragraphs

Please be more aware of this for any other posts.
It’s also one of the rules.

Thanks

 

[jeffhuey1n]

Wow!

How often must one rig the flight controls? I’m sure the answer depends on flight time, but was there a general rule of thumb (monthly, annually, etc.)?

How long does it take a skilled mechanic to do the rigging?

There’s various reasons for checking rigging. A rig check is mandatory every time a component in the flight controls is repaired or replaced. At certain times, such as a 200 hour phase inspection, a rigging check is mandated. Another reason is if there is a uncommanded input into the flight controls, a rig check must be performed.
The experience level of the mechanic plays an important part in rigging. As a highly qualified UH-1N/HH-60/HH-3E and CH/HH-53’s, I could get a rigging job done relatively quick. A trained but inexperienced mechanic could take days to get the job done. I never participated in rigging the CH-46
nor the CH-47. The 46’s (AKA Phrog) and the 47’s have two main rotor heads. There’s going to be difficulties for anyone person to accomplish all the tasks required.

 

[Tinstar]

The experience level of the mechanic plays an important part in rigging.

Spot on statement.

 

[m715mike]

What is an “uncommanded input into the flight controls”?

 

[charlesmann]

What is an “uncommanded input into the flight controls”?

An input the pilot didn't make. Sometimes that could contributed to an AFCS (automatic flight control system) computer issue, or in the case of our's yesterday, grit and or petroleum collection. Excess grease from the last time the pedal boxes were lubed was not cleaned up. A bit of dirt got between the pedal control bellcrank and the roll axis bellcrank.

When the meat servo moved the pedals, the cyclic would move in the roll axis slightly. The roll movement during pedal movement would be considered an uncommanded input. As could a sticking rod end bearing, within a similar mixed control unit, causing 1 input to move another axis within that particular mixing unit.

Another could be from slack in a cable controlled component, like the tail rotor control in a blackhawk. The elevator or rudder control surface in a small fixed wing, such as a cessna 152. The improper adjustment of the cable tension could allow for air moving over the airfoil to send feedback movement to the control input devise, be it pedals, yoke (for fixed wings) and cyclic (for helicopters), causing it to move.

Enough time in a specific machine, some pilots can feel the slightest variations/vibrations in a control surface that would be considered "abnormal" and have it checked out by the maintenance crews.

 

[jeffhuey1n]

An example of uncommanded input is from my CH-53 days. In the automatic flight control system there are servos that must be correctly positioned in order for pilot inputs to be accurately sent to the rotor systems. There are various servos, each one is detailed for a particular flight movement. Pitch, Altitude, Roll and Yaw. The acronym is “PARY”. If a valve is worn, the metering valves can become misaligned. You want to lift the collective stick a certain distance for a particular flight movement. When the valves become misaligned, small stick maneuvers can create incorrect signals being sent the the flight controls. You want to go forward. You manipulate the controls so that you should move in that direction. Instead, you move and your controls do something “abnormal”. Lifting the collective and you move backwards unexpectedly. Rigging is almost an art.