Venturis
Posted: Thu Oct 15, 2020 1:04 am
Just have been reading some old posts on venturis and found it was a very interesting topic . My aircraft has fitted a dual venturis 9in and a single Venturi of 4in. This was the set up on the aircraft since I have owned [20 yrs] and haven’t any problems . The aircraft has a AH and a DG which has supplied vacuum air for both instruments . Both venturis are plumbed into the same manifold . Idle the vac gauge shows about 1.5 ins and both instruments are nearly up to speed On take off ,no issues what so ever . In cruise it’s about 4.5 ins . But there is no vacuum regulator . Both instruments were overhauled about 4 years ago and it appeared to be the first overhaul for both instruments . One of the large venturis is made of bronze . Now the third Venturi provides vacuum for the “bat and ball” turn indicator . It provides about 2ins of vacuum, this 3rd Venturi [4in] is also made of bronze . Manufacturer unknown. When COVID 19 restrictions are removed [when ????] I will be fitting a garmin G5 . However the small Venturi has another task which makes me very reluctant to remove it. It produces a high pitched whistling noise below 90 kts . I have flown over people at 500 ft and they hear it on the ground . Many have said I have a bad exhaust leak or exhaust gasket blown . It’s this 4in Venturi . Why?? I do not know BUT this high pitched whistle frightens off the kangaroos off the runways . Kangaroos in Australia are in plague numbers and eat the grass on the runways and drink water in the drains near the runways . They have become very used to the movement of aircraft . It’s a problem at many ALA,s. I noticed on some of my landings ,the kangaroos would move off the runway as I approached . After a couple of experiments to trace this noise I also noticed the kangaroos would “take off” as I taxied past them . [no George ,kangaroos do not have wings]