|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

06-21-2015, 08:53 AM
|
 |
|
|
Join Date: Mar 2005
Location: Dallas area
Posts: 10,769
|
|
Actually the alternate air doors on the "snorkels" are quite successful.
Many people have built alt air doors that slide open manually. These are also quite successful.
It's mostly the "passive" style of doors that fail.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
|

06-21-2015, 10:20 AM
|
 |
|
|
Join Date: May 2009
Location: Fort Mill, South Carolina
Posts: 345
|
|
Quote:
Originally Posted by Vlad
Make a poll Bruce would be interesting to see how many RVs don't have it.
I don't. 
|
Of all the people who might actually experience a blockage of their intake, due to birds/branches/balloons/flying fish/small children?YOU ARE IT, my friend! 
__________________
Bruce Windom
QB RV-8 N148BW
First Flight: Oct '16
AeroSport Power IO-360 180hp w/dual P-Mags
Catto 3-blade, with black carbon spinner.
10" Dynon SkyviewTouch. That's ALL.
2020 Dues contributed
|

06-21-2015, 11:58 AM
|
 |
|
|
Join Date: Jan 2005
Location: SC
Posts: 12,887
|
|
There are risks with everything we do, or not do.
Why is the option of adding the alternate air door available? It is my understand it was to give a pilot an "option", if the air intake iced up.
If that is the case and you don't fly IFR in icing conditions, leave it off, as I did.
If you are worried about sucking in a plastic bag on takeoff, I doubt you will have time to sort out what is going on in time to open the alternate air door before hitting the trees at the end of the runway. Not to mention, what are the real odds of that happening? (I understand it has happened but again, what are the odds?)
In the early days, the air door was held shut by a small magnet and if the main intake was blocked, the suction of the engine would allow the door to open automatically. (I have always wondered if it would open at high power settings while on the ground, just when you need filtered air the most.) The problem was that some of them came apart and some of those parts were sucked into the engine. That little problem lead to the current manual door and even some of those have come apart.
In short, you roll the dice and take your chances.
Since I was building a VFR ship, I left it off and in 650+ hours of flight, I have never given it a second thought.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
|

06-21-2015, 04:51 PM
|
|
|
|
Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,167
|
|
 [ Here is what we have. It's clean and simple. I don't see how any failures could introduce FOD. The barrel rotates and opens the slots as a alternate source of air. I believe it is a ECI system.
George
Last edited by sailvi767 : 06-21-2015 at 04:59 PM.
|

06-21-2015, 05:19 PM
|
|
|
|
Join Date: Mar 2008
Location: houston, texas
Posts: 900
|
|
Two cents.
I'm with Mel on this, and have learned the hard way in the certified world that ALT. air is a very good thing to have. Everyone knows carb. icing. It is induction icing that can and does trip a few up with an injected engine. It has been a long time now that I have not been around the factory guys. Maybe Mel knows off the top of his head but I think it used to be required for a Part. 23 build program.. We have a snorkel and won't leave home with out checking to be sure our ALT-air door works. We made it out of the Van's kit, but made it so it will reset in flight and not fall apart..
My two cents. Yours. R.E.A. III # 80888
|

06-21-2015, 05:41 PM
|
 |
|
|
Join Date: Jan 2005
Location: SC
Posts: 12,887
|
|
Quote:
Originally Posted by Robert Anglin
...Everyone knows carb. icing. It is induction icing that can and does trip a few up with an injected engine. ...
|
Only one thing, what we are talking about won't help with carb icing as the alt air still goes through the carb or fuel servo for injected engines.
All this does is bypass the air filter in the event the air filter gets plugged.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
|

06-21-2015, 06:43 PM
|
 |
|
|
Join Date: Sep 2006
Location: Defiance, MO
Posts: 1,674
|
|
I think this thread has a mix of answers and opinions on two slightly different subjects; alternate air (blocks off main air intake and opens to pull air from inside cowl but still goes through filter) and filter by pass (opens hole in bottom of FAB in the middle of filter to draw air from cowl into induction without going through the filter.)
I have taken off and covered over the filter by pass door since there has been plenty of trouble with the various designs and the risk of parts going into engine too great for any benefit of getting air to engine if filter clogged. I still have my alternate air door even though I have had to replace the hinge and fix it several times because I feel it has benefits. It has little risk of parts going through the engine if it fails because the filter will stop it.
__________________
Philip
RV-6A - 14+ years, 950+ hours
Based at 1H0 (Creve Coeur)
Paid dues yearly since 2007
Last edited by plehrke : 06-21-2015 at 06:55 PM.
|

06-21-2015, 07:21 PM
|
|
|
|
Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
|
|
While your definitions are perhaps 'cleaner' or clearer, they re not the customary ones. Virtually every normally certificated aircraft that I've seen labels the knob 'alternate air' when in fact it is a filter bypass.
|

06-21-2015, 07:59 PM
|
|
|
|
Join Date: Jul 2007
Location: Cypress, TX
Posts: 526
|
|
Filter bypass on the bottom of the FAB. No problems and it works well and seals tight. I made a ring so it is riveted thru metal on both sides of the fiberglass. What is the failure mode?
|

06-21-2015, 10:15 PM
|
 |
|
|
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
|
|
Quote:
Originally Posted by Ironflight
It is a risk trade - the risk of the intake becoming blocked versus the risk of the door coming apart and FODing the engine. The anecdotal evidence suggest that there are many more cases of the various versions coming apart than there have been blockages (although they HAVE occurred -apparently rarely). I have personally seen so many air boxes that have shaken and vibrated themselves apart that, for me, the blockage is a lower probability than the mechanism failing - so I dont have alternate air doors an any of our current RV's.
Everyone should make their own choice.
|
Agreed x 1000
I wish we did not have one, but we do, although having the FOD problem, we made a fabricated aluminium (aluminium for you guys  ) air box and it has been great.
And we avoid icing conditions in a non FIKI aircraft.
__________________
______________________________
David Brown
DYNON Authorised Dealer and Installer
The two best investments you can make, by any financial test, an EMS and APS!
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 08:44 AM.
|