Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ihnp3.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!ihnp3!cfiaime
From: cfiaime@ihnp3.UUCP (Jeff Williams)
Newsgroups: net.aviation
Subject: re: spins and SKIDS
Message-ID: <158@ihnp3.UUCP>
Date: Fri, 20-Sep-85 13:13:48 EDT
Article-I.D.: ihnp3.158
Posted: Fri Sep 20 13:13:48 1985
Date-Received: Sat, 21-Sep-85 04:39:11 EDT
References: <1877@bmcg.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 63
Summary: Flap usage in Cessna aircraft

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


Brought to you by Super Global Mega Corp .com