Helicopter rotor blades have to be balanced to cut back vibration that may place stress on the helicopter’s airframe. At FRCE, this balancing course of has historically been carried out utilizing the ability’s Helicopter Blade Stability Facility, generally often called a whirl tower, to simulate the blade’s efficiency in flight.
“Usually, if you stability a blade, you’re utilizing a bodily grasp blade,” mentioned Joshua Peedin, senior rotor programs engineer for the H-53 Fleet Assist Crew (FST). “You test it in opposition to a static balancer, you then run it on the tower to bear in mind the dynamic masses. The aim is to make the blade weigh and fly much like the grasp blade.”
Nonetheless, the whirl tower at FRCE doesn’t have the scale or the horsepower to accommodate the size and weight of a CH-53K blade; that’s the place the common static stability fixture, or USBF, is available in.
“The USBF fixture creates a digital grasp the place the identified parameters, dimensions and traits of the grasp blade are entered into the software program,” mentioned Peedin. “Whenever you weigh a major rotor blade, it compares the info in opposition to the digital parameters to inform you how you can regulate the blade and what weights so as to add or subtract.”
The artisan then provides weights to the tip finish of the blade, in positions that have an effect on the lengthwise weight of a blade or the way it will pitch ahead and again. This course of have to be exact; the load distinction attributable to sanding or making use of a restore can spell the distinction between balancing a blade or sending it again to the producer for stripping and rebuilding.
The USBF is at present used to stability H-53E major rotor and tail blades, in addition to blades for the V-22 Osprey and H-1 Viper and Venom plane. The system has carried out so effectively that the upkeep plan for the brand new CH-53K mannequin requires its rotor blades to be examined on the USBF, in line with FRCE engineers.
The choice whether or not to undertake the USBF system required intensive testing with the intention to collect and analyze knowledge, mentioned Peedin.
“We used the info we procured whereas testing H-53E blades to validate the method,” he mentioned. “As we stepped by means of and eventually examined it on plane, everybody grew to become snug sufficient with the outcomes to take away the whirl tower requirement from the CH-53K upkeep plan in favor of the USBF.”
The USBF system’s reliability and relatively low buy and upkeep prices are anticipated to assist FRCE meet the fleet’s wants for economical upkeep methods for the H-53K program, in line with Daniel Ventry, CH-53K lead system engineer on the H-53 FST.
“The addition of this technique is among the initiatives that this system is investigating to cut back the whole life cycle price of the brand new acquisition program,” Ventry mentioned. “As we develop the technique for the life cycle, considered one of our tenets of this system technique is to make sure that the long run sustainment of this system is as price efficient as potential.”
FRCE engineers and artisans say the static fixture is extra dependable than the whirl tower, which will be affected by wind, rain or vibrant daylight. As well as, crane upkeep may also be a think about whether or not the whirl tower can be utilized on a given day. Conversely, the USBF is housed in a climate-controlled constructing with 4 overhead crane programs accessible to be used.
“Simply the opposite day, I had blades up and I acquired a name from the [air traffic control] tower saying there was a gust of wind coming at 30 knots,” mentioned Robert Name, work chief for the dynamic elements store. “I needed to run on the market and take them down, or the wind might snap a blade. I can run blades on the brand new fixture it doesn’t matter what the climate.”
Not like the whirl tower, FRCE has a backup USBF fixture accessible to be used in case the first system requires upkeep or restore. The H-53 Program Workplace procured two USBF fixtures to mitigate any potential downtime that might outcome from an inoperable system, mentioned Zackary Barnard, rotor blade store lead engineer at FRCE. As well as, with a price ticket of $170,000 per unit, engineers say the USBF system is extra economical than the whirl tower in the long term.
“The price to run the tower, so far as energy draw and upkeep, is round $500,000 a 12 months,” Barnard defined. “The USBF doesn’t have these prices.”
The programs are additionally moveable, which makes them accessible to deployed items. Engineers say this skill to stability blades will permit fleet maintainers to carry out extra blade repairs on website.
“There are some repairs the fleet couldn’t carry out as a result of the blade needed to be balanced afterward,” Peedin mentioned. “Now they’ll have the potential to stability the blade relatively than sending it again to FRCE for balancing, which suggests they will do extra repairs themselves.”
FRCE engineers are hoping the brand new system will give them forecasting skill to find out the result of repairs earlier than the work is finished. The plan is to make use of the info collected from the USBF to create a “cheat sheet” to find out how a lot a restore will be anticipated so as to add to the load of the blade.
“That approach, after I consider a blade, I can see that blade has XYZ weights on it, and when the plane examiner recommends a restore, we’ve a playbook that claims this restore weighs this a lot,” Peedin mentioned. “You possibly can see how the blade is at present weighted and get an informed guess as as to if we will nonetheless stability the blade when that is completed.”
Engineers say this preplanning will assist eradicate the money and time spent on unsuccessful repairs.
“There’s at all times a priority with blades that want a number of repairs that we’ll put within the effort for a restore solely to search out we will’t stability the blade because of the further restore weight,” mentioned Barnard. “It will permit us to know whether or not a blade can finally be balanced earlier than we carry out the repairs.”
Peedin mentioned adopting the static stability fixture system for the CH-53K blades has taken a while to validate, as a result of the whirl towers have such an extended historical past of balancing blades. Nonetheless, he mentioned the suggestions the USBF system is getting makes his efforts in advocating for the system worthwhile.
“My largest satisfaction was after we acquired the primary two items right here, and we began placing blades on them and getting constant knowledge,” Peedin mentioned. “Quite a lot of effort has gone into procuring this technique, and it’s gratifying to see proof that we’re getting into the appropriate route.”
FRCE is North Carolina’s largest upkeep, restore, overhaul and technical providers supplier, with greater than 4,000 civilian, navy and contract employees. Its annual income exceeds $1 billion. The depot gives service to the fleet whereas functioning as an integral a part of the larger U.S. Navy; Naval Air Programs Command; and Commander, Fleet Readiness Facilities.
