Most of my MEP on Piper, athough a fair bit on DA42. Most SOP is Alternate Air in visible moisture below 5oC and icing. The alternate air on the PA-30 is spring loaded, and the manual back up control is checked on pre take off checks.
There is a performance penalty asymmetric with alternate air.
A feature of DA42 TKS is it tends to fade on the wing tips and allows some ice contamination ahead of the ailerons.
Some airplanes have automatic alternate air doors, The Mooney 201 and I believe the 231 as well. I don’t know about others but it sure makes sense
Mooney_Driver wrote:
Some airplanes have automatic alternate air doors,
Same for the C210, BE55 etc. Don’t know about the Twinkie.
As above the PA-30 has automatic alternate air.
I have automatic alternate, but no manual override, or indication of it’s status, which I do dislike.
However it’s not an item I’ve ever heard referred to in any incident, so perhaps it’s considered a good and reliable design.
RobertL18C wrote:
As above the PA-30 has automatic alternate air.
Again learned something here. I didn’t know that the spring loaded alternate air operates automatically, but I read through the technical specifications and it turns out to say the same. The spring force is quite noticeable, I wouldn’t have thought that it operates against that force.
RobertL18C wrote:
As above the PA-30 has automatic alternate air.
Now I’m confused. If it’s automatic, why does the checklist say Alternate Air – Full ? Does the PA30 have a manual way to open/close alternate air in addition to the automatic gate?
Yes!it can manually override. I thought it was only manually, but no!
Source AOPA.org
A 1,200-hour private pilot attempted to climb his Comanche 260 with four passengers on board through a layer of severe icing. A sigmet warned the pilot of severe ice from the surface to 12,000 feet. The engine intake clogged with ice at 5,000 feet, and the alternate air apparently was not used or didn’t work. The flight landed in a parking lot without injuries to anyone.
Does this sound a little familiar?
