The Executive Director of the Cessna Pilots Association (who is a 210 owner and A&P/IA himself) tells Centurion owners what they need to know to stay out of trouble.
January 9, 1996
Dear Cessna 210 Owner,
FAA records indicate that you recently registered a Cessna 210 aircraft. I am writing to brief you on several
safety-critical topics that we believe every Centurion owner should be aware of. Our experience indicates that
many 210 owners (even some experienced ones) are not aware of certain important characteristics of this
aircraft. Without this knowledge, it is possible to get into serious trouble.
In this letter, I'm going to talk to you about idiosynchrasies of the Cessna 210 fuel system, retractable landing
gear, and several other aircraft systems. If you are new to Cessna Centurions, I'm sure you'll find this
information enlightening. If you are an old hand with Centurions, you may still find it a worthwhile review.
At the end of this letter, I'm going to tell you a little about the Cessna Pilots Association and urge you to
become a member of this valuable technical information service for Cessna owners. But whether you decide to
join CPA or not, I want you and your passengers to be safe when you fly your Centurion. So please take a few
minutes to read over this material carefully.
BLADDER WRINKLES. If you fly a strut-braced 210 (1960 through 1966 model years), your
airplane uses rubber bladder tanks in each wing. These bladders have a tendancy to develop wrinkles along the
bottom. The wrinkles act as little dams that can prevent water from moving to the sump drain. This means that
you can sump the tanks at preflight and see no water, yet dangerous amounts of water could still be present in
your fuel tanks.
To make matters worse, Cessna originally installed flush-style fuel caps on these aircraft. These caps have a
tendency to leak if the aircraft is exposed to moisture. If your fuel caps have a small hinged pull-up handle that
fits into a recess in the cap, you have the dangerous fuel caps. At CPA, we call them "killer caps."
There have been a number of engine failures after take-off in these aircraft due to water ingestion even though
the pilot sumped the tanks thoroughly during pre-flight. Some of these incidents have been fatal. The FAA
issued Airworthiness Directive AD 84-10-01 to deal with this problem. It requires inspection of the bladders
for wrinkles, and suggests changing flush-style fuel caps to umbrella-style caps.
If you fly a bladder-equipped 210 that still has flush-style fuel caps, the Cessna Pilots Association strongly
uges you to change immediately to either the Cessna umbrella cap (kit SK182-85 available through any
Cessna dealer) or the Monarch Development cap.
BUT THE LINEBOY SWORE HE TOPPED THE TANKS! If your 210 is a
cantelever-wing model (without struts, 1967 through 1986 models), it uses integral fuel tanks. This basically
means that several bays in each wing are sealed to serve as a fuel tank, with the top and bottom wing skins
forming the top and bottom of the tank.
Because the fuel tank is long and flat and has a recessed filler port, it can be difficult to get the last few
gallons of fuel in each tank. The tank may appear full when it is actually 5 to 10 gallons short. There have
been a number of off-airport landings caused by fuel exhaustion because the pilots thought the tanks had been
filled but were actually short of full by a significant amount.
This problem can be reduced by installing non-recessed fuel caps, using Cessna kit SKxxx-xx or Monarch
Development caps (phone xxx/xxx- xxxx). If you order the Monarch caps, make sure to get the latest raised
caps and not their older screw on caps. The FAA has also issued AD xx-xx-xx, applicable to all cantelever-
wing 210s, which requires calibration of the aircraft's fuel gauges, notation in the aircraft records, and in some
cases placards at the fuel filler ports.
Any time you make a flight of 4 hours or more, you must be 100% positive that you have full tanks. To
accomplish this, you must fuel the aircraft on a level surface. Your nose strut must be inflated sufficiently to
give the aircraft a slightly nose-up attitude (about 4.5 degrees for most models). Fill each tank until the fuel in
each tank is all the way up to the upper wing skin. Then wait several minutes, re-check the fuel level in each
tank, and add more fuel if necessary.
SO THAT'S WHAT THOSE TWO HOLES ON THE BELLY ARE FOR! On all
Cessna 210s, the main fuel tanks feed into small reservoir tanks. Their purpose is to provide the fuel injection
system a source of fuel undisturbed by aircraft attitude, and to receive excess fuel and vapor that is returned
from the fuel control unit.
Models prior to 1982 have two reservoir tanks, one for each wing tank, that are located in the belly of the
aircraft beneath the floor boards. From 1982 on, the 210 fuel system was changed so that only a single
reservoir tank is used. The reservoir tanks can collect water and sediment. They should to be drained at
preflight prior to the first flight of the day. This is frequently overlooked. The reservoir tanks have quick
drains. (Early models originally had drain plugs installed in the reservoir tanks, but an A.D. mandated that
these be retrofitted with quick drains.) In some cases, the holes for access to the quick drains have "Wilkie"
buttons installed in them. These can be removed and discarded to provide easier access to the drains.
THE LOUDEST SILENCE IN THE WORLD. The Centurion has a history of fuel flow
fluctuations and, in a few cases, engine stoppage due to vapor lock. This has been most prevalent in
turbocharged 210s from the early 1970s through the 1981 model year. The problem occurs when the reservoir
tanks become filled with fuel vapor instead of liquid fuel. Turbocharged aircraft are more vulnerable because
they climb rapidly to altitude and have higher engine compartment temperatures. Normally-aspirated 210s
seldom develop this vapor lock problems in-flight. If they do, it is usually an indication of a mechanical
problem within the fuel system.
The important thing to remember is that while the reservoir tank on the side of the fuel tank in use is filling
with vapor, the opposite-side reservoir tank is full of liquid fuel with no vapor. If you suspect a vapor problem,
switch fuel tanks and turn the boost pump to low. This will almost always stabilize fuel flow and restore
engine power. There is also a modification that can be performed to the T210 exhaust system that reduces the
heat soaking of the fuel in the engine compartment.
Another vapor-related topic is the infamous problem of hot starts on fuel injection engines. The Cessna Pilots
Association has developed a sure-fire hot-start proceedure that works every time, and does not involve
flooding the engine (which can be a fire hazard). CPA members may obtain this hot-start handout at no charge.
RETRACTABLE LANDING GEAR
The Centurion landing gear system has a lousy reputation. Actually, the gear system can be extremely reliable
if you and your maintenance shop understands the system thoroughly. CPA's three-day Cessna 210 Systems
and Procedures Course devotes several hours to this subject, but I will mention a few of the highlights
UH OH! NO GREEN LIGHT. If you don't get a green light after extending the gear, the first thing
to do is to visually check the landing gear position. When down and locked, the main gear tires can be seen
from the cabin. However, the nosewheel is not visible to the pilot unless you install a convex landing gear
mirror. A mirror is also necessary to observe the position of the main gear doors (if your plane has them). CPA
sells an STC'd mirror that simply replaces one of the underwing inspection plates.
If the landing gear appears completely down but there is no green light, a normal landing should be made. If
the main gear is down but not quite locked, the weight of the aircraft will push the main gear legs toward the
locked position. However, the nose gear retracts forward, so weight on an unlocked nose gear will tend to
make it retract. Therefore, take care to hold the nose wheel off the ground as long as possible.
If the gear does not appear to be fully extended, try to determine the cause. On 1971 and earlier 210s which
use an engine-driven hydraulic pump, recycle the landing gear handle to the neutral position and then back to
the down position. On 1972 and later 210s with an electrically-driven hydraulic pump, make sure that the
landing gear switch is in the down position and that neither the landing gear motor circuit breaker or landing
gear control circuit breaker have tripped.
If the gear still is not fully extended, then it is time to use the emergency extension system. With the landing
gear handle or switch in the down position, pull out the emergency extension pump handle and start pumping.
Continue until the handle feels like it is set in cement. Visually determine that the gear is extended and that
you have a green light, then make a normal landing.
If the emergency extension handle won't budge, the most likely cause is a stuck door solenoid valve (assuming
you have doors). The door solenoid valve is electrically activated to the door-closed position and spring-
loaded to the door-open position. Try turning off the master switch (VFR conditions only!) to allow the
electrical circuits in the landing gear system to cool down. This may allow the solenoid valve to drop into
place. You can also try pulling the plastic center console cover off to expose the landing gear power pack, and
rap on the door solenoid valve to encourage it to release. The door solenoid valve is the small silver canister
assembly on the left side of the power pack.
If the emergency extension handle moves freely but the gear does not extend, the most likely cause is
insufficent hydraulic fluid. On pre-1972 aircraft, there's not much you can do other than verifying that this is
the situation by observing if any fluid is visible through the sight glass. On 1972 and later models, there's a
dipstick and filler port behind a removable panel on the center console. If the dipstick shows no fluid in the
power pack, you can try pouring any available liquid into the power pack reservoir.
IF NOTHING WORKS, KEEP YOUR COOL. If a gear-up landing can't be avoided, the
important thing is not to panic. A landing with the gear up or partially extended is not a life-threatening
situation and only through panic can a pilot turn it into one. Simply make a normal approach, touching down
at as low an airspeed as you are comfortable with while maintaining control of the aircraft.
If you are faced with making a wheels-up landing, here are some items you might want to keep in mind:
JUST LIKE KIDS WHO WON'T CLOSE DOORS. The most common 210 landing gear
complaint I hear is "I retract the gear but the doors won't close!" Because many shops really don't understand
the system, owners have paid for many needless repairs, power pack overhauls, and door-removal
modifications. Actually, there is a simple electrical circuit involving the the up-lock and down lock
microswitches along with the handle switch that energizes the door solenoid valve to the door-close position.
If your doors won't close on either the gear-up or gear-down cycle, then the problem is in this circuit and
should take less than an hour to troubleshoot.
Contrary to intuition, less damage will be done touch down
on smooth pavement than on grass.
Pavement is better than grass.
If you disturb airline schedules, the airport
management will want toclear the runway quickly, which could result in greater damage to your aircraft. The
FAA may get upset, too. If the wind is manageable, consider using a crosswind runway at an airport you think
you might have repairs done.
Pick a runway the airlines don't need.
The hangar flyers will tell you should shut
down the engine and stop the prop on final to minimize damage. Most of those guys have never done it. I have,
and let me tell you it is no easy task. Once you pull the mixture out to shut down the engine, you will have to
reduce airspeed almost to stall to get the prop stopped, and then remain at very low airspeed to prevent the
prop from windmilling again. What's the point? At best, you'll only be saving money for your insurance
company. And that's a pretty poor reason for increasing the risk factor during a wheels up landing.
Don't worry about prop or engine damage.
IS PLASTIC KEEPING YOUR NOSE UP? Your nose gear has a little "downlock spring guide"
to retain a spring that keeps tension on the nose gear downlock hooks. When Cessna originally built your
aircraft, they installed a spring guide made entirely of plastic, with two plastic pins that fit into holes in the
downlock hooks. These plastic pins have a tendency to break, and this can result in the downlock spring
falling out and leaving no tension on the downlock hooks. Taxi over a bump and the nose gear could collapse.
Cessna came out with an improved guide, P/N xxxxxxxx, which has steel pins instead of plastic ones. All
210s were manufactured with the all-plastic guide, so unless you have a log book entry that shows installation
of the improved part, your aircraft is in jeopardy. The new part costs about $15 and takes about an hour to
change. It's a very small price to pay to avoid a costly nose gear collapse.
BACK IN THE SADDLE AGAIN. 1960 through 1969 210s have flat spring steel landing gear
legs held in "saddles". Service history indicates that these saddles can crack over time, creating the possibility
of a landing gear failure. The FAA issued AD XX-XX-XX which requires annual dye-penetrant inspection of
these saddles after a certain number of hours. The Cessna Pilots Association reccomends the saddles be
checked every 100 hours or at annual inspection no matter how many hours are on them.
ALL YOU WANT IS CLEAN AIR. On turbocharged 210s, the exhaust heat exchanger uses spiral
fins to improve cabin heat capacity. Unfortunately, the heat exchanger tends to develop cracks where the fins
welded to it. Such cracks can allow dangerous exhaust fumes into the cockpit. The FAA issued AD 71-XX-
XX which requires pressure checking the exhaust system of all turbocharged 210s EVERY 50 HOURS! This
is an important and often overlooked inspection.
DON'T SHAKE YOUR TAIL FEATHERS. Cessna 210 often develop cracks at the attach points
for both the vertical and horizontal stabilizers, particularly at the "station 209 bulkhead" where the forward
spar of the horizontal stabilizer attaches. This area needs to be inspected very carefully. Cessna offers service
kits to strengthen these areas.
ROTTEN TRAILING EDGES. Cessna built the trailing edge of the 210 elevator and the entire
elevator trim tab with a foam core. It seemed like a good idea at the time, but it wasn't. The foam core absorbs
moisture which causes the elevator trailing edge and the trim tab to corrode from the inside out. By the time
you see the tell-tale bubbling of the paint on the trim tab or elevator trailing edge, the structure is seriously
compromised. Cessna now offers replacement parts that do not use a foam core.
AND NOW...A WORD FROM YOUR
The Cessna 210 Centurion is a great aircraft. In its later variations, it is arguably the best single-engine
travelling machine ever built. But as with any mechanical device, time and service have shown that there are
areas of concern that owners/operators need to be aware of. Which is why CPA exists.
The principal purpose of the Cessna Pilots Association is to provide our members with in-depth technical
information about their aircraft that is simply not available anywhere else. CPA members receive our monthly
CPA Magazine; each 32-page issue is jam-packed with late-breaking news, technical articles, details of new
ADs and service bulletins, service difficulty reports, general aviation alerts, and other vital Cessna-specific
CPA also has developed a long list of informational handouts that deal with the most frequently-seen
problems and frequently-asked questions about Cessnas: nosewheel shimmy, hot starts, oil on the belly,
uneven fuel feeding, and many other subjects. These handouts are available at no cost to CPA members.
One of the most valuable aspects of CPA membership is unlimited access to the CPA Technical Hotline. CPA
is the only Cessna owners association with a full-time staff of A& P mechanics available daily to answer
your questions. Each one is a real Cessna expert. We also maintain the largest Cessna technical library outside
of the Cessna factory. If you need help troubleshooting an elusive problem or locating a hard-to-find part, we
can help. We can also save you big money on high-ticket parts by telling you where to get the best deals.
If you join CPA and call with a 210-related problem, you'll probably wind up talking to me. One of my jobs at
the Cessna Pilots Association is to provide technical support to our members who own 210s. In addition, I
operate and maintain my own T210 (a 1967 model). I know the aircraft intimately and can answer almost any
210 question you might have. If I don't know the answer myself, I know who knows!
CPA also offers a terrific three-day Cessna 210 Systems and Procedures Course. The seminar is given several
times a year at the CPA Technical Center in California, and once a year in several other parts of the country.
Our instructors are some of the foremost 210 experts in the world. After you graduate from this course, you
will know more about your Centurion than 99% of all 210 owners, and you'll probably understand its complex
systems (particularly landing gear and electrical) better than most A& Ps do. There is no better way to
learn so much about your aircraft so quickly.
I hope you decide to join the Cessna Pilots Association. It costs just $40 to for the first year, and $35 to
renew. Most of our members feel that CPA membership is one of the best bargains in aviation.
But whether or not you choose to join CPA, please pay careful attention to the information in this letter,
particularly the cautions about fuel contamination and fuel capacity. The 210 has a history of fuel-system-
related accidents. A little knowledge and caution will prevent you from adding to the statistics.
Let's all of us be careful up there.
John M. Frank