Narrative:

I went on a training flight with a student to practice short field takeoffs and landings. The flight over to the airport was uneventful. The day was perfect from an aviator's point of view; sky clear; visibility greater than ten miles; no turbulence; and the wind was blowing 340 at 8 KTS; the preferred runway was 35; making for relatively little crosswind. Student landed fine the first time; with the roll-out being ok other than the nose gear 'shimmy.' the aircraft used has a free-castering type nose gear; similar to the front wheels on a shopping cart. In certain conditions; the gear will shimmy. We taxied back to the active; only to be called out by another aircraft on the CTAF; 'hey; aircraft that just landed; your nose gear seemed to be shimmying badly.' I responded that it was ok; and that is was normal for this type of aircraft. Student and I went around again; and despite a bounced landing (student was having trouble with the flare and sight picture); the landing seemed ok. However; on the roll-out; the same thing happened; and the nose gear shimmied even worse. Another aircraft called us out on the CTAF; 'hey; I saw that too; and that thing looks unsafe; you should really have that checked out.' I told my student that is seemed to be shimmying much worse than normal; and decided that it was best to go back home and have the gear looked at. Upon landing at the home airport; we had discovered that the gear had somehow managed to turn nearly 120 degrees into the prop arc; causing a strike and a chopped up nose gear pant. While the investigation is ongoing on why this happened; there are some key things I'd like to address: 1. The mechanics said that the nose gear should not turn beyond a set number of degrees (I believe 90-100??); the aircraft in said question has always been able to turn a full 360; which I thought was normal; but now I find out is not. Did this cause the shimmy; which in turn caused the gear to enter the prop arc? 2. The mechanics also pulled up a diagram of the nose gear for the aircraft; and the kind of nose gear installed on the aircraft is of a different design than what the manufacturer states should be on the aircraft. Again; did this possible mis-installed/redesigned nose gear cause the shimmy; which in turn caused the gear to enter the prop arc? 3. My student did bounce the final landing at the other airport; but it did not seem that bad; after all; I have had a few students bounce a landing in this particular aircraft with no issues. Was this a 'once in a million shot' that caused the nose gear to enter the prop arc? 4. How could the nose gear even enter the prop arc to begin with? With airflow going over the nose gear pant; the streamlined shape of it should cause it to align with the relative wind; forcing it aft; like it should be. How could it have entered the prop arc if we were in flight; with the relative wind supposed to be aligning the gear with the relative wind (aft)? What I have learned; if somebody calls me out on something that seems abnormal; I will next time attempt to stop what I am doing and assess/inspect the situation; rather than just simply pass it off as just 'uninformed observations;' as it is probably a warning if multiple other people notice something abnormal.

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Original NASA ASRS Text

Title: A SR20 had an incorrect nose landing gear installed which allowed the gear to rotate 180 degrees and during a nose wheel shimmy event the propeller struck the nose wheel pant.

Narrative: I went on a training flight with a student to practice short field takeoffs and landings. The flight over to the airport was uneventful. The day was perfect from an aviator's point of view; sky clear; visibility greater than ten miles; no turbulence; and the wind was blowing 340 at 8 KTS; the preferred runway was 35; making for relatively little crosswind. Student landed fine the first time; with the roll-out being OK other than the nose gear 'shimmy.' The aircraft used has a free-castering type nose gear; similar to the front wheels on a shopping cart. In certain conditions; the gear will shimmy. We taxied back to the active; only to be called out by another aircraft on the CTAF; 'Hey; aircraft that just landed; your nose gear seemed to be shimmying badly.' I responded that it was OK; and that is was normal for this type of aircraft. Student and I went around again; and despite a bounced landing (student was having trouble with the flare and sight picture); the landing seemed OK. However; on the roll-out; the same thing happened; and the nose gear shimmied even worse. Another aircraft called us out on the CTAF; 'Hey; I saw that too; and that thing looks unsafe; you should really have that checked out.' I told my student that is seemed to be shimmying much worse than normal; and decided that it was best to go back home and have the gear looked at. Upon landing at the home airport; we had discovered that the gear had somehow managed to turn nearly 120 degrees into the prop arc; causing a strike and a chopped up nose gear pant. While the investigation is ongoing on why this happened; there are some key things I'd like to address: 1. The mechanics said that the nose gear should not turn beyond a set number of degrees (I believe 90-100??); the aircraft in said question has always been able to turn a full 360; which I thought was normal; but now I find out is not. Did this cause the shimmy; which in turn caused the gear to enter the prop arc? 2. The mechanics also pulled up a diagram of the nose gear for the aircraft; and the kind of nose gear installed on the aircraft is of a different design than what the manufacturer states should be on the aircraft. Again; did this possible mis-installed/redesigned nose gear cause the shimmy; which in turn caused the gear to enter the prop arc? 3. My student did bounce the final landing at the other airport; but it did not seem that bad; after all; I have had a few students bounce a landing in this particular aircraft with no issues. Was this a 'once in a million shot' that caused the nose gear to enter the prop arc? 4. How could the nose gear even enter the prop arc to begin with? With airflow going over the nose gear pant; the streamlined shape of it should cause it to align with the relative wind; forcing it aft; like it should be. How could it have entered the prop arc if we were in flight; with the relative wind supposed to be aligning the gear with the relative wind (aft)? What I have learned; if somebody calls me out on something that seems abnormal; I will next time attempt to stop what I am doing and assess/inspect the situation; rather than just simply pass it off as just 'uninformed observations;' as it is probably a warning if multiple other people notice something abnormal.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.