Air box question

The picture shows an air box on a 160 HP Tri-Pacer. Have also seen the same cross reinforcement on air box on 160hp Apache. 1) Is this for better airflow or just reinforcement of the air box? 2) Next if it’s for airflow then is this why there seems to be less carb ice on Cubs using the long air filter and do all Cubs with the long air filter have that cross reinforcement in their air boxes?
Thank You


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It straightens out the swirling air from unequal length intake tubes on Lycoming 320s.

Thanks Steve
Do you feel that it is that much of a benefit to replace an existing air box if it doesn’t have one on a 160 O320?


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I don't know, no data from one vs the other.

They’re commonly called crossvanes and the purpose is to straighten the air out instead of swirling through the carb Venturi. An old friend tested with and without them on an Apache years ago. He said without them the engine didn’t run very well due to 2 rich and 2 lean cylinders. I had the same problem on my RV-4 and crossvanes fixed it. Yes different length intake tubes on A and B 320s contributes to it too.

1
FAA
Aviation Safety
SPECIAL AIRWORTHINESS
INFORMATION BULLETIN
SUBJ: Engine Air Intake System; Air Box Vanes
SAIB: CE-13-26
Date: March 27, 2013
This is information only. Recommendations aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) alerts you, owners and operators of all
Lavia Argentina S.A. (LAVIASA) Model PA-25 (type certificate formerly held by Piper
Aircraft, Inc.) airplanes and Piper Aircraft, Inc. Models PA-25, PA-28-140, -150, -160 and -180
airplanes, of an airworthiness concern, specifically that the vanes of induction system air boxes can
break off in flight and lodge into carburetors, which would restrict air flow and reduce engine power.
At this time, this airworthiness concern has not been determined to be an unsafe condition that
would warrant AD action under Title 14 of the Code of Federal Aviation Regulations (14 CFR) part
39.
Background
The vanes in the air boxes of the airplanes referenced above are welded into the throat of the air box
by the air box’s carburetor mount. The vanes are essential to reducing turbulent air flow entering the
carburetor in flight. Without their presence, an engine may run rough at altitude. The vanes are not
for structural support and their removal is not recommended.
In September of 2012, a vane broke off from the air box of an affected airplane used for agricultural
purposes and lodged into the airplane’s carburetor, which resulted in a forced landing and substantial
structural damage. The report we received indicated the time in service (TIS) of the air box had
exceeded the engine time between overhaul (TBO). We have since received a report of pilots preemptively
removing air box vanes to prevent such incidents in other airplanes. Currently, there are
no requirements or recommendations to inspect vane welds in air boxes that have a TIS greater than
engine TBO.
Recommendations
For the owners and operators of Model PA-25 airplanes, all serial numbers, and Models PA-28-140,
-150, -160 and -180 airplanes with serial numbers 28-1 thru 28-1760, the FAA recommends the
following when the air box TIS reaches engine TBO or before further flight if air box TIS is already
over engine TBO, and thereafter at each annual inspection:
1. Remove the air box. .
2. Visually inspect all vane welds with a light source and mirror and record results and airplane
TIS.
3. Replace or repair an air box exhibiting cracks within and/or adjacent to the vane welds and
record the airplane TIS.
4. Do not remove the vanes from the air boxes of airplanes so equipped.
2
For Further Information Contact
Gary Wechsler, Aerospace Engineer, Atlanta ACO, 1701 Columbia Ave., College Park, GA 30337;
phone: (404) 474-5575; fax: (404) 474-5606; email: gary.wechsler@faa.gov

Thanks everyone for your reply’s. One more question with regard to that type of air box with the cross vanes. After looking at a number manufacturer’s websites for a new replacement we can’t seem to find any new air boxes with the cross vanes installed. Since the information bulletin indicates that you shouldn’t remove the vanes if you have them how do you replace a worn out box?
Still a few more places to check but any suggestions on where to look would be appreciated. Thanks again.

Poor Joe said:

Thanks everyone for your reply’s. One more question with regard to that type of air box with the cross vanes. After looking at a number manufacturer’s websites for a new replacement we can’t seem to find any new air boxes with the cross vanes installed. Since the information bulletin indicates that you shouldn’t remove the vanes if you have them how do you replace a worn out box?
Still a few more places to check but any suggestions on where to look would be appreciated. Thanks again.

Click to expand...

Send that worn out air box to Randy Rubbert. He'll make it better than new.

MTV