I'm in the process of buying a '52 170B and was looking at the flaps today. I'm moving up from a 140 and the 170 has real flaps! They seemed to have a lot of play in them when fully extended unlike the 140's which are spring loaded. Is this normal? Is it expensive to replace the bushings?
Thanks
Troy
1952 170B Flaps
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
-
GAHorn
- Posts: 21302
- Joined: Fri Apr 12, 2002 8:45 pm
The Cessna "Para-lift" flaps do indeed have considerable free-play when in any position except up. (In fact, they are allowed a little slack there as well, but air pressure holds them up against the stops in flight.)
How much play? Generally, about 1/2 inch or less movement at the trailing edge. If movement is much greater than that (and anytime you're performing a "pre-buy" or annual, you should inspect for wear at the rollers and flap-tracks. The flap-track curved slots should never be allowed to wear beyond .6035". (A 19/32 drill bit shaft will fit into the slot but if a 39/64 does then the track is worn beyond specs and must be replaced.) Most guys don't have drills in this range, but to give you an idea, a 5/8 bolt is so large that if it fits into the slot you've got tracks grossly UN-airworthy. What the average guy MIGHT have is a set of feeler gauges such as used for measureing valve clearances and ignition point clearances. (In any case, a set of feeler gauges are cheap to purchase at any automotive parts house or supplier, and can be used for other purposes than drilling odd-sized holes.) Slipping a feeler guage between the flap rollers and the track should allow you to check for excess wear in the flap-track and/or rollers. The no-go measurement you're looking for is .040". Any gap exceeding that anywhere along the track indicates tracks, rollers, or both needful of replacement.
Also slide the flaps span-wise to see if they will contact either the aileron or the wing-root fairing or if either flap-bracket contacts the flap-track itself. If it does, then the flaps are either assembled incorrectly without the correct spacers (common AN washers) at the outboard rollers, or they've been damaged and improperly repaired. See the Illustrated Parts Catalog (IPC), fig 6. As a potential 170 owner you DO have the IPC don't you? It's virtually req'd equipment in my opinion, available from the seller or from Aircraft Spruce 877/477-7823.
How much play? Generally, about 1/2 inch or less movement at the trailing edge. If movement is much greater than that (and anytime you're performing a "pre-buy" or annual, you should inspect for wear at the rollers and flap-tracks. The flap-track curved slots should never be allowed to wear beyond .6035". (A 19/32 drill bit shaft will fit into the slot but if a 39/64 does then the track is worn beyond specs and must be replaced.) Most guys don't have drills in this range, but to give you an idea, a 5/8 bolt is so large that if it fits into the slot you've got tracks grossly UN-airworthy. What the average guy MIGHT have is a set of feeler gauges such as used for measureing valve clearances and ignition point clearances. (In any case, a set of feeler gauges are cheap to purchase at any automotive parts house or supplier, and can be used for other purposes than drilling odd-sized holes.) Slipping a feeler guage between the flap rollers and the track should allow you to check for excess wear in the flap-track and/or rollers. The no-go measurement you're looking for is .040". Any gap exceeding that anywhere along the track indicates tracks, rollers, or both needful of replacement.
Also slide the flaps span-wise to see if they will contact either the aileron or the wing-root fairing or if either flap-bracket contacts the flap-track itself. If it does, then the flaps are either assembled incorrectly without the correct spacers (common AN washers) at the outboard rollers, or they've been damaged and improperly repaired. See the Illustrated Parts Catalog (IPC), fig 6. As a potential 170 owner you DO have the IPC don't you? It's virtually req'd equipment in my opinion, available from the seller or from Aircraft Spruce 877/477-7823.
Cessna® is a registered trademark of Textron Aviation, Inc. The International Cessna® 170 Association is an independent owners/operators association dedicated to C170 aircraft and early O-300-powered C172s. We are not affiliated with Cessna® or Textron Aviation, Inc. in any way.