CheckSix Forums

In an email to Defense News, AFSOC public affairs director Lt. Col. Becky Heyse said that the command’s 52 tiltrotor Ospreys were grounded on Tuesday due to recent “hard clutch engagement” incidents. Two such problems have happened in the last six weeks, and there were previously two others that occurred since 2017

The clutch inside a gearbox that connects one of the CV-22’s two Rolls-Royce Liberty AE1107C engines to the propeller rotor is slipping for an unknown reason, Heyse told Breaking Defense, which first reported the stand-down on Wednesday.

TOPOLO a écrit : ↑

jeu. août 18, 2022 10:42 am

Vu les hélice des V-22, il y a forcément un embrayage entre les turbine et les hélices (je ne sais pas si c'est le cas pour tous les turbo-prop, mais je vois mal lancer la turbine en entrainant l'hélice, même sur un PT-6)

De fait, tout arrêt de l'un de ses moteurs expose potentiellement l'équipage à la perte de l'appareil. Il est cependant équipé d'un système de couplage croisé (cross shafting), de lignes d'arbres d'interconnexion, permettant d'assurer la synchronisation des deux rotors ou la répartition de la puissance d'un seul moteur sur les deux rotors, en cas de défaillance de l'autre moteur. L'ensemble étant sous le contrôle du système numérique de commandes de vol, triplement redondant

zeufman a écrit : ↑

jeu. août 18, 2022 5:13 pm

c'est trés intéressant cette video
, du moin interpellant
voici ce que dit Wikipedia

De fait, tout arrêt de l'un de ses moteurs expose potentiellement l'équipage à la perte de l'appareil. Il est cependant équipé d'un système de couplage croisé (cross shafting), de lignes d'arbres d'interconnexion, permettant d'assurer la synchronisation des deux rotors ou la répartition de la puissance d'un seul moteur sur les deux rotors, en cas de défaillance de l'autre moteur. L'ensemble étant sous le contrôle du système numérique de commandes de vol, triplement redondant

This problem occurs when the clutch, which connects the propeller’s rotor gear box to its engine, slips. That causes the Osprey to transfer the power load to the other engine almost instantaneously so the aircraft can keep from crashing.

The original gear box’s clutch then reengages, the power load transfers back in a span of milliseconds and the large transfer of torque causes the Osprey to lurch, the Air Force said.

The V-22 program has experienced a total of 15 instances of hard clutch engagement, including 10 in Marine Corps Ospreys, since 2010, the defense official said. The Navy confirmed Thursday it has not experienced this problem with its CMV-22 variant, which is the newest in the Osprey fleet and began its first deployment last August.

Air Force Special Operations Command today cleared its CV-22 Osprey fleet to resume operations, but pilots will be required to operate using a series of risk-mitigation techniques in order to avoid a safety issue related to the engines on the rotorcraft.

The problem in question, according to AFSOC, is a “hard clutch engagement” or HCE. Basically, the clutch inside a gearbox that connects one of the CV-22’s two Rolls-Royce Liberty AE1107C engines to the propeller rotor is slipping for an unknown reason. When that happens, the power load transfers nearly instantaneously to the other engine — a design feature that would allow the Osprey to keep flying even if one engine fails. Then, in most cases, the initial clutch re-engages, and the power load rapidly shifts back to the original propeller rotor and engine.

As a result of the rapid movement of power across engines, the aircrew is forced to land the CV-22 immediately, and a spokeswoman noted on Aug. 17 that “if the aircrew were unable to control the aircraft when the incident occurs, it could result in loss of control and uncontrolled landing of the aircraft.”

U.S. military officials have imposed new operating restrictions on the Bell Boeing V-22 Osprey tiltrotor fleet. Issue linked to vertical takeoffs and gearbox age CV-22 remains...