fredc@bmcg.UUCP (Fred Cordes) (09/16/85)
Sorry about the mis-information. I dug a book on glider instruction to verify that the stall-spin condition I referred to occurs from skids, not slips. The "under the bottom" on final is the situation I was trying to reference. As for 40 degree flaps blanking the tail, I was told that by 2 instructors (I flew with with 5 instructors in 4 years before I got my ticket...) that this condition occurred and was the reason for limiting 152's to 30 degrees max. I can't find anything in the manuals either but I'll keep looking. I was alos told that a 150 cannot climb with 40 degrees flaps down. I have had the experiance of having the flaps go to full down on takeoff. The limit switches were bad and I had set the flaps for 10 degrees for short field takeoff. The instr. was with me (he's not the one that warned me) and noticed that we weren't climbing- from looking outside by the way. We had enough altitude to do a 180 and land on the same runway. We were weren't climbing well at all, but we were climbing. It was fairly close to "std day" conditions so I cannot account for it due to den alt. I've tended to believe all of my instructors, but they do differ a lot on theory and practice. The gent who rents his 150 to me these days has been flying more than 40 years, and refuses to use more than 20 degrees flaps on approach (his tires...) and instructed me to (biennial) use long low approaches with power. He called my high, gliding, incremental flap patterns "Aeronca landings". So now I end up with a high approach and only 20 degrees flaps and usually have to slip the plane a lot to get it down. I may not appear too proficient but it sure is fun! fred cordes
cfiaime@ihnp3.UUCP (Jeff Williams) (09/20/85)
Oh the perennial Cessna 150 flap question. (This is a bit of a flame because of instructors who DON'T KNOW WHAT THEY ARE TALKING ABOUT!) The Cessna 150 has 40 degrees of flaps using the same basic planform as the L-19 flap (except the L-19 had 60 degrees). These are a single slotted modified Fowler, either electric or manual depending on the year of the airplane. There are NO aerodynamic problems that arise from using the full 40 degrees of flap available on a Cessna 150. The "Avoid Slips With Full Flaps Extended" placard applies to the Cessna 172. On the 172, if you slip with full flaps using full rudder and necessary aileron to match the rudder input with an aft CG, you will get an uncommanded pitch oscillation of up to 5 degrees. The pitch oscillation is annoying, not dangerous. Hence the placard. On the Cessna Para-lift Flap (and that is a trademark, however I haven't seen them use the term for a while), the first 20 degrees give a dramatic increase of lift with little increase of drag. The last 20 degrees give an increase of drag with almost no increase of lift. Therefore, when you use 10 to 20 degrees of flaps for landing, you are going to INCREASE your landing distance because your airplane is going to FLOAT. And if you are a typical pilot who adds 10 knots for wife and kids, you are going to float a LONG WAY. Especially on a hot day. (Oh why don't people fly the recommended speeds for landing?) As an example, there was a Doctor (comments aside) who managed to put a brand new Cessna 172 through the fence at the end of the 5000 foot runway by adding 25 knots to the recommended final approach speed, and using 10 degrees of flaps. Moral of the story: use the recommended final approach speed and FULL flaps (or 0 flaps if in a HEAVY crosswind). As for the fact that the new 172 and the 152 have only 30 degrees of flap is because of the high accident rate with the 40 degree flap. Not in the landing phase, but in go arounds. It seems that very few people know that the airplane WILL climb with full flaps, but that you need to hold your speed at the BOTTOM of the green arc. The climb is sluggish and you may need to land off airport (assuming a flap retraction failure), but you will not have an airplane that will refuse to climb. (This, of course, depends on density altitude, engine condition, and pilot technique. There are some density altitudes that the airplane will not climb no matter what you do. Like above the service ceiling altitude.) As for the gentleman who was criticized for his "Aeronca landings," the fact that you now have to make massive slips to land shows that the technique you were taught is wrong. Hasn't your instructor heard of stabilized approaches? As for instructors, it is easy to lose touch with currant thinking on subjects aeronautical. Many instructors renew their ratings by showing past performance of students. An instructor should attend a refresher clinic every couple of years, or spend some time with the FAA on new techniques. (My CFI gets renewed annually when I take my CAP Chief Check Pilot ride with the FAA. The oral for the ride takes around 3 hours, typically talking of problem areas such as flap misusage or takeoff techniques.) I am open for private mail or public discussion on any of the topics raised here. jeff williams ihnp3!cfiaime
jeq@laidbak.UUCP (Jonathan E. Quist) (09/22/85)
In article <1877@bmcg.UUCP> fredc@bmcg.UUCP (Fred Cordes) writes: >As for 40 degree flaps blanking the tail, I was told that by 2 instructors >(I flew with with 5 instructors in 4 years before I got my ticket...) that >this condition occurred and was the reason for limiting 152's to 30 degrees >max. I can't find anything in the manuals either but I'll keep looking. A while back, I mentioned this problem with my 1961 172. The first time I tried 40 degrees flaps, the tail kicked out to one side. The previous owner tells me that he had this problem at first, until he figured out that when he was pulling full flaps (this bird has manual flaps with a __long__ handle) he was twisting a bit in his seat and his feet were moving on the pedals. Soo, next time I was up, I again tried a 40 degree landing, paying close attention to my feet. Sure enough, the tail stayed straight, and she landed slow as can be. I did notice a bit of pitch oscillation, which the manuals do mention, but it was not what I would call objectionable. Jonathan E. Quist ihnp4!laidbak!jeq, jeq@N7656X ``I deny this is a disclaimer.''