I didn't realise how much interest my inflight adjustable cowl flaps would
create - 15 requests for the photos so far. Mark Jackson has offered to put
them on his website so to avoid everyone having to put up with a large
download I will pass them on to him for publishing.
The essence of the mod is as follows:
A pair of apertures (240mm x 40mm) were cut in the lower rear of the cowl
just forward of the footwell protrusions of the firewall. External
overlapping flaps (5 plies of 'bid') with full length aluminium hinges were
fitted to the cowl. The flaps were held closed using springs attached to
the inside of the cowl forward of the flaps at one end and a bracket on the
rear inside of the flap at the other. The bracket also helps to stiffen the
flap to prevent distortion. An extra Rotax dual choke cable (supplied by
Europa Aircraft) was utilised for control. It has two Bowden cables mated
to a single control knob (labelled 'COWL FLAPS') enabling adjustment of
both cowl flaps simultaneously. The outer sheaths of the cables are held at
their lower ends to the vertical forward face of the footwells using
clamps. Friction adjustment was achieved by the use of a screw tapped into
the body of the control knob assembly. The cables can be locked in position
by twisting the knob (similar to the manual choke used in older cars). The
lower end of the cables are terminated with solderless nipples which are
attached to ends of a pair of belcranks. The other end of the belcranks
have small wheels attached which push against the flaps as they are
rotated. This type of interconnection was used so that there was no
permanent connection between the cable and the cowl easing cowl removal and
refitting (see photos for design details). If this is difficult to
understand the photos should reveal all.
NB. As every Europa tends to be a little different in its cooling
requirements it pays to get the cooling set correctly for cold weather
operation with the flaps closed first. The flaps are then just used to
provide an increase in cooling for hotter weather. Be aware that they will
only have limited effect for extended ground running due to the limited
airflow.
Nigel Charles
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