Chinook - Still Hitting Back 3 (Merged)

[John Blakeley]

Speeds

Dalek,

You raise a very interesting comment on aircraft speeds. As it happens in the last day or so I have been "delving" into a BD report PE/CHINOOK/41 dated 22 October 1993, which was jointly signed by the then Superintendents of Flying and of Aircraft Dynamics, and which is one of several additional reports called up as being an essential element of the Interim CA Release Recommendations. As far as I know none of these reports were assessed by the BoI.

Paragraph 21 of this report says:

Flight Envelopes The aircraft's handling characteristics were assessed briefly throughout the flight envelope up to 5000ft at AUMs up to 19000 kg. As with the Mk 1 aircraft, the maximum speed and manoeuvring capability were limited by the need to keep the Cruise Guide Indicator (CGI) in the Green segment, with only transient excursions into the Yellow band during turns. The aircraft handling characteristics were essentially unchanged from the Mk 1. As speed was increased the vibration characteristics of the aircraft increased significantly. The A&AEE Vibration Assessment Rating Scale was used to assess cockpit vaibration levels. At approximately 130 kn IAS, the vibration became more noticeable at VAR 5 (Moderate - Experienced aircrew are aware of the vibration but it does not affect their work at least over a short period.) and as the speed was increased to maximum possible with the CGI on the edge of the Green band, 150 kn IAS, the vibration was rated as VAR 7 (Severe - Vibration is immediately apparent to experienced aircrew even when fully occupied. Performance of primary task affected or tasks can only be done with difficulty.) During all the tests conducted the maximum flight envelope speeds were not reached as the CGI approached the Yellow band, with transient excursions into this band, before reaching Vmax. The vibration characteristics were similar to the Mk 1 and were unsatisfactory.

Assuming that ZD 576 exhibited similar vibration characteristics to the BD trials aircraft it seems to me as a "simple" engineer that the crew were very unlikely to have deliberately flown at some of the claimed speeds - especially given the VIPs in the back, but I will happily "bow" to more expert opinion.

JB