One main-rotor servoactuator was intact enough to allow bench testing. Dis- assembly of the two remaining main-rotor servos found no internal damage.
The Takeaway All evidence indicates that the helicopter was airworthy up until the moment of upset. Although both pilots were highly experienced and very familiar with the local environment, they chose not to climb away from a ridgeline buffeted by stiff, per- pendicular winds and the rotor currents they generated, despite seeing indications of sharp local downdrafts. Transport Canada recommends post- poning mountain flights if the winds at the peaks are forecast to exceed 30 kt.; the FAA suggests a 25-kt. limit. The FAA also recommends pilots climb to at least 1,000 ft. above a ridge at least 3 mi. before reaching it. Not wanting to climb to, say, 4,000 ft. on a 21-nm flight is
understandable, but greater separation from what the TSB characterized as the “complex terrain” of Howe Sound would likely have helped the pilots to avoid the worst of the resulting turbulence. The pilots’ confidence in the forecast of
improving conditions may also have been misplaced. By 10 am, about 10 minutes after the accident, winds at Pam Rocks had increased to a base velocity of 36 kt., with gusts up to 52. Between 9 and 10 am, the wind at Vancouver International Airport had likewise increased, from 19 kt. with gusts to 26 to 26 kt. with peak gusts of 38, conditions unfriendly if not down- right inhospitable. As severe as this accident was, it’s also
worth noting that some things went right. The cargo line, hook, and nets were all secured in the cabin and remained stowed, but various small items were car- ried in an open milk crate lashed to the cabin floor. These became projectiles
when the helicopter departed controlled flight. The TSB report draws attention to the
fact that both pilots wore flight helmets of recent vintage that incurred significant damage from the impact of those objects, thereby protecting the pilots from severe head injuries and enabling them to evacu- ate quickly after the crash. The use of flight helmets and four-point restraints helped limit the severity of their injuries. Most crucial is the fact that despite the damage inflicted by the bumping episode, the main-rotor mast held together until the helicopter reached the ground. The FAA notes that “turbulence, especially severe downdrafts,” is a known cause of the low-G conditions in which two-bladed tee- tering rotors are susceptible to mast bumping. Fracture of the main-rotor mast, of course, is generally not survivable, so on that point these two aviators were for- tunate indeed.
601 - REMOTE HOOK SHOWN WITH STANDARD GUARD
901 - REMOTE HOOK SHOWN WITH EXTENDED GUARD
909 - PRIMARY HOOK STC'D FOR THE BLACKHAWK/UH-60
MANUFACTURER OF WORLD CLASS REMOTE AND PRIMARY CARGO HOOKS FOR MORE THAN 30 YEARS I HOOK OVERHAULS: FLAT RATE $525. FAST TURN-AROUND! 1000 85TH AVE. SE OLYMPIA, WA 98501 I PHONE: 360-754-7200
I
SALES@MECHSPECIALTIES.COPM I
WWW.MECHSPECIALTIES.COM DECEMBER 2022 ROTOR 55
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
