HeliTrak is now selling its collective pull down system for the Robinson R22, having received an FAA supplemental type certificate (STC) last October and FAA parts manufacturer approval (PMA) on February 9. The collective pull down (CPD) is designed to lower the collective rapidly and automatically in a low rotor rpm situation.
The CPD is HeliTrak’s first product, and now that it is on the market, the company is developing a CPD and an autopilot system for the R44. Other helicopter types, such as the Airbus EC135, will also be fitted with the CPD, according to HeliTrak president Chris Nehls. R44 CPD flight testing began just before this year’s Heli-Expo. While the R22’s rotor system is considered to be a low-inertia system, HeliTrak (Booth 8531) believes that the CPD can benefit any type of helicopter.
The CPD attaches to the collective and can be switched on or off, depending on the pilot’s preference or for whether instructors want to use it during training. “It works fine if you want to train with it, or disable it and do a normal autorotation entry,” said Nehls.
In the R22, said Ray Debs, HeliTrak flight test pilot and v-p of engineering, “the collective has to go down immediately, you have half a second.” Then the pilot has time to move the cyclic to maintain rotor rpm. “If you don’t do aft cyclic, you’re going to lose rpm. The normal reaction is to try to hold attitude. When the CPD fires, it’s pretty normal to move the cyclic to maintain attitude. You’re not trying to pull the nose up. In this aircraft, cyclic has big impact on rotor rpm, and if you use cyclic to keep the nose constant, it works well.”
Debs explained that during flight testing, it was critical to lower the collective, then apply cyclic as needed to maintain rotor rpm. “My belief is that collective is critical in all cases,” he said. “The benefit [of the CPD] is that it gives the pilot two or three more seconds to figure out what to do. In all of our tests, rpm hasn’t gone below 90 percent. The low warning is at 97 percent. Robinson says if you go below 80 percent you won’t be able to recover. Even if you don’t react on the cyclic immediately, you still have a good safety margin [with the CPD]. The pilot has to do the right thing eventually, but the CPD gives him time.”
The CPD’s pull-down force can be adjusted to to pilot’s preference, between 6.5 and 10 pounds of force; Debs prefers 7.5 pounds. The pilot can override the CPD, he added. “If they override it, they can feel it. They should be thinking that something’s going on, and they need to do something different,” such as move the collective down.
The R22 CPD will retail for $14,950, but HeliTrak is offering promotional pricing at $9,950, with lower pricing for HeliTrak dealers.
The R44 autopilot is a parallel system with no series actuators, using triplex motor drives and ADAHRS. Total weight of the self-contained system is 8.5 pounds. All control buttons are mounted on the helicopter’s cyclic, and features include heading-, altitude- and speed-hold modes, speed protection in altitude hold and an unusual-attitude recovery mode. Nav modes and coupled approaches will be added next year, to facilitate IFR training. HeliTrak expects the R44 autopilot to sell for half the price of competing products.