_ 12 - E
The mayorlty of this fllght was made clear of all clouds However, the evldencf 1ndlcates that moderate lolng was possible 1n the clouds 1n the Kansas Clty area from,6,000 feet down to approximately 3,500 feet. Whlle no determlnatlon can be i made of water droplet Size or water denSLty 1n the cloud, the temperature ranges in the cloud were those whmfllhavebeen establlshed by tunnel tests as hav1ng been con— . duclve to the formatlon of horn type rlme lee. The tunnel testlng 1nd1cated that from 10 to 20 minutes was requlred to establlshkunvrllke lee formations of the SlZB descrlbed by wltnesses However, a Contlnental Alr Llnes pllot's testlmony 1nd1cate€ that this type of 1L8 formation can occur w1th1n 2 or 3 minutes. CAL 290 was 1n 1c1r condltlons from 6-8 mlnutes, long enough to have acclmulated 1ce as descrlbed by ‘ other Viscount crews and developed durlng the tunnel tests. The testlng by the man- ufacturer 1ndlcates that the operatlon of either one of the two heat exchangers 3 produces sufflclent heat at the tallplane to prevent 1c1ng even under the extreme { condltlons tested. Heat applied lollowlng a bulldup of horn type lee wlll remove I
i i
2
the ice 1n one minute or less. Runback ice may form under certain condltlons of de-101ng (as opposed to ant1—1c1ng), and during the tests rldges of as much as 3/4 inch was produced. These tests dld, however, show that there was no apprec1able change 1n elevator hlnge moment from thls type formation. The weather 1nformatlon furnlshed to the crew indlcated moderate to heavy 1c1ng over southern Kansas and Oklahoma, but did not call for 101mg 1n the Kansas C1ty terminal area However, the terminal forecast did indicate cloudiness ln the Kansas 01ty area wlth SUb-fPeBZlng temperature at the surface. Assunlng that the captain followed the establlshed company procedure for dalng the Wlfldshleld heat ln the low peeltnon throughout the flight it 13 possible that no 1<e World iorm on the windshield. ThlS 1s normally the first 1nd1catlon the crew has that ice ls forming on the alroraft. Testlmony an testlng have lndacated that the only way a horn type oi 1C8 formatlon could occur on the horizontal stabllizer would be if the oo-lclng system were not used 1n fllght through the clouds, or if the system had lulled and no heat was prov1ded to the tall surfaces. There is no evidence to substantiate a failure of the antJ—lclng system. The crew should have expected JCLHg 1n the clouds However, as was the case with the Colorado Sprlngs crew, 1f the wandshleld anti—lolng system was on they may never have seen any jud1catlon of ice on the alrcxaft and therefore not turned on the alr- foll anti-nelng system.
The alrcraft was suhyected to an extremely rade nosedown pltchlng moment that could only have been applied by nosedown elevator or by a loss of down loadlng on the tall. However, altitude was not aufilcxent to allow the requ1red amount of pater down by p110t actuated elevator control alone None of the other pltch control mechanisms on the alrcraft could have prchded suff101ent rotatlon to force the air- craft into a 22—degree nosedown prtch attitude wlthln the altltude avallable at the time of the noseover.
The Board bellevcs that flaps were lowered to 20 degrees at some pelnt durlng the approach; most probably at or near the outer marker. The lee shape was such that thlS amount of flap, at the alrspeed involved was not detrlmental to aircraft trim. The remalnder of the approach was made at 20 degzees of flaps until over the runway. When over the runway the power was reduced and the flaps were further extem Probably to 40 degrees. When the crew Jea11Zed that a landlng could not be made, Power was applied for a go~arolhd, toe ilaps were raised to 32 degrees, and the gear handle was actuated. As the alrSpBed arorcased the nosedown pltchlng moment 1noreafi to a pelnt where 1t could no longer be counteracted This may have been due to eijh E Progre551ve loss of negatlve 11ft or a tall stall 1nduced by extreme up elevator. At this pelnt the alrcraft pltched over and crashei.
