The installing a Lycoming 0-320 engine
to replace the stock Continental 0-200 engine is a moderately popular
conversion for Cessna 150 airplanes.
As in all engineering designs there
compromises must be made. When compared to a stock 150 the 150/150
has significantly enhanced performance numbers but at the cost of
additional weight and fuel burn.
As would be expected the addition of an
additional 50 horse power to a 100 horsepower airplane produces some
significant changes in performance. The most notable performance
change is in climb. The stock 150 is not known for its’ ability
to climb. A 50% power increase completely changes the picture.
The 150/150 will climb like the proverbial homesick angle. The
increase in cruise performance while substantial is not nearly as
spectacular as the improvement in climb performance.
After all is said and done a 150/150 is
sill a Cessna 150, with muscles. The weight and balance restrictions
and the V speeds are the same. No a 150/150 does not stall at a
higher speed, it still has a gross certified
weight of 1600
Why Would Anyone
Want a 150 HP Cessna 150?
There are probably more reasons for
having a 150/150 than there are 150/150s. Just a few reasons that
come to mind are:
A 150/150 makes a fine banner tow
A 150/150 can be used to tow
A 150/150 is an excellent patrol
aircraft. It is as fast or faster than a
172, lower operating cost and is more maneuverable.
A 150/150 is a great plane for
getting in and out of short strips.
A 150/150 is a hot rod. Not
real fast on the big end but quick to get started.
A 150/150 is much like a sports
car, nimble, quick on the controls with good performance.
A 150/150 is a good choice for
high elevation airport operations.
A 150/150 is just plane fun. (pun
If you think that you might like to have
a 150/150 but are not sure get a demo ride.
How Does a
The thing that a 150/150 does best is
CLIMB. The table below gives the climb performance of my airplane
equipped with a Sensenich 74”X53”
climb prop. The data was obtained by conducting three timed climbs to
the airplane’s service ceiling. The data from each climb test
were averaged and the results were linearized
using the least square fit method.
OF CLIMB IN FEET PER MINUTE
OF CLIMB IN FEET PER MINUTE
The prop makes a huge difference in the
climb performance. When the same series of flight test were performed
using a 56”
pitch prop the climb rates were 25% less than those with the 53” pitch prop.
Cruise performance is important to all
of us. If we wanted to go slow we would get a Cub. The table
below gives the cruise performance data at 75% power for my plane, equipped
with a “climb prop”. It is interesting to note that there
was little loss in cruise speed at low altitude and a slight increase in
cruise speed at altitudes above 9000’ when the prop was re-pitched
This is most likely due to the fact that the engine will turn faster at
higher altitudes and allow more power to be developed.
The cruise data is the result of
averaging the results of three timed five mile speed runs.
Can One Get a 150/150?
Purchasing a 150/150
There are two legal ways to get a
150/150, build one or buy one.
At any given time there are a
handful of converted 150s advertised for sale. The asking price for
150/150s runs from a low of $18,000 to a high of over $50,000. There are currently 150/150 listed for sale on the Cessna
150-152 Club web site and in Trade-A-Plane. When purchasing a 150/150
the same attention to the condition of the airplane as with any other
purchase is necessary. In addition to the normal items to look for
like engine condition, corrosion, paint, interior, etc. it is highly desirable to obtain ALL of
the paper work pertaining to the conversion, including the STC drawings.
When you purchase a 150/150 you
get a certified, flying airplane that you can fly right now and upgrade, if
required, on your time and fiscal schedule.
The other way to obtain a 150/150 is to
do the modification yourself. This will entail at a minimum buying an
airframe, an engine, a prop, a spinner, the STC, the installation kit, and
numerous bits and pieces, then locating a shop that is capable and willing
to install the conversion. Next comes the waiting and added expenses
while the shop makes the installation and finds all sorts of little things
what will need to be resolved, all taking time and costing money.
There will also be additional
items that you will most likely like to add at the time of the
conversion. Since the 0-320 is thirstier than an
0-200 long range tanks while not an absolute necessity are a convenient
item if you plan to use the plane for cross country travel.
There are a couple of companies
that hold STCs for the 150 HP conversion.
Or at least there were two a few months ago. Aircraft Conversions
Technologies and Robert and Barbara Williams, DBA as Avcon
or Bush, both hold conversion STC. More about them later.
Obtaining the engine is not an
easy task. The STC calls for a Lycoming 0-320-E2D. While these
engines are by no means rare you can’t get one at the 7-11 store. The prices and conditions will vary greatly
and one will have to be very careful in order to obtain a good value in a
used engine. Of course you can always go with a new engine. $$$ Ouch!
the prop and spinner. A used prop will be very difficult to locate
and a new one will most likely be required. Again $$$ Ouch! The
spinner will be available from the 150 HP conversion STC holder
but most likely will not come with the kit.
When you get all of the big chunks
gathered up you can load it all in your little red wagon and haul it out to
your conversion shop. The STC holders will give you an estimate of
around 90 to 100 hours to make the conversion. In my experience
unless the shop that you are using is well experienced in making the
conversion these numbers are way low. For your budget add 50% to 100%
to the STC holder’s estimated labor cost.
When the conversion is completed
carefully monitor the paper work and be sure that there are 337s for all of
the major items.
Where Can I Get The Conversion Kits?
are three sources for STCs and conversion
Aero Upgrade LLC
8252 Cessna Drive
O Box 25272
Talk to Harry Dellicker
Barbara and Bob Williams
Bush Conversions (Avcon
O Box 431
The Williams are very nice people and
provide quality product with good documentation and are very helpful.
They are however a little slow to respond. The last quote on delivery
that I got from them was six weeks. I honestly can not recommend
their company because of chronically slow service.
Auxiliary Fuel Tanks?
For a plane that is going to be used for
cross country travel long range or auxiliary fuel tanks are a very nice
option. Running the 0-320 at 75% power will consume 8.4 gallons per
hour. With stock fuel tanks you have 22.5 gallons of
usable fuel. That translates to about 2:40 to dry tanks. If you
land with a VFR legal thirty minutes of fuel remaining you will have an
effective range of around 275
miles in no wind conditions.
there was a lot of interest in and questions about my 150/150 and 150 HP
conversions in general. Since I have returned home I have had a
number of email inquiries about the conversion. The following is an attempt
to answer as many of those questions as possible. I hope that Jeff and some
of the other 150/150 drivers will chime in and flesh out the points that I
miss of correct me where I am wrong.
It should be noted that I have only
accumulated around 60 hours of flying in my little airplane since I started
flying it in March. I have learned a lot but I still have a lot to learn.
Steve can tell you that I still can't spot land it worth a hoot, I smacked
of the mythical A/C carrier at Clinton.
For me one of the most important issues
when considering an engine conversion is will the resulting airplane fit my
needs. I want an airplane that will allow me to make cross country trips of
200 to 500 miles
without the need to RON. Where I live it is necessary to fly high to avoid
getting beat up by turbulence in the spring and summer. My home
airport is 2800 MSL and our second home airport is at 6800 MSL. I need to
be able to take off at gross weight when the DA is above 9000'.
Most important of all since I have
retired I need an airplane that will perform all of these
task at a relatively low capital cost and with a low operating cost.
For the last 25 years I have been flying complex airplanes with big bore
engines. The $3000 insurance bills
$4000 annual inspections/maintenance have priced those birds put of my
My decision to get into a 150/150 came
after a couple of years of study and consideration.
A stock 150 just does not have the power
plant to meet my needs.
A 172 was my first choice but it has
very anemic performance at high altitude. I own half of a Cherokee 140/150
with my son but again it does not climb well or perform well at high
altitude. (I flew a Cherokee for over 1500 hours and an well acquainted
and shortcomings.) The 180 HP 177 is a little better performer than the 172
and Cherokee but not a lot.
A 182 performs well at altitude but the
capital cost and operating cost are just too high for my budget.
While the 150 is small in most aspects
it has essentially the same wing as the 172.
When the same engine is installed on a plane with 600 to 800 pounds of weight
you get a plane that will CLIMB!
With insurance for a 150 at $500 per
year and annual inspection cost at $500 per year. The 150/150 started to
look good. Now add the fact that the 0-320 has a 2000 hr TOB and that a
good overhaul can be had for $10,000 as opposed to the 1200 hr TBO and
$25,000 overhaul cost for a TSIO-520 and it looks even better. On my normal
200 nm the 150/150 burns 14 gallons of fuel
as opposed to 22
gallons and the picture becomes clear. Sure the trip
will take an extra 25 minutes but that is a small price to pay for the
economic benefits. What would I rather do with those 25 minutes than
The decision was made. The 150/150 fit
my mission profile to a tee and it is a plane that I can afford to own and
fly. I decided to do the conversion rather than buy a converted airplane. I
was really planning on a 180 HP 0-360 conversion. After I purchased my
1973L I found what seemed like a very good deal on a 1968 H 150/150 so I
bought it too. We later found that the H model had BAD corrosion in the
right wing and the decision was made to jack up the STC and drive the L
model under it. I lovingly call the result my Sport Hawk.
In addition to adding the 150 HP engine
there were a number of other mods added. Each of
these items was installed to fill a specific requirement.
The most often asked question is
"How do you like your 150/150". The answer to that question is
easy, I love it. It performs pretty much as I expected. It will get off of
the runway at 9000' DA in a reasonable distance and climb out at around 700
With the current prop (that is a whole 'nother story) the Sport Hawk at rated gross weight will
climb from 3,500' to 17,000' DA in 26 minutes. While not a blinding rate of
climb it will get me up in to the cool, smooth air in a reasonable time.
Cruise speeds at 75% power run from 120 MPH TAS at 1500 feet to 137 MPH TAS at 12,500 feet density
altitude. At 75% power the 0-320 burns 8.4 GPH (source Lycoming). Dropping
the power to 65% reduces the fuel flow rate to 7.3 GPH and will reduce the
cruise speed by around 5
Pulling the black knob back to 50%
drops the fuel flow to 6 GPH and farther reduces the cruise speed by
another 5 MPH.
Note: 50% power for the 0-320 is equal to 75% power for the 0-200.
The next most often question is
"How much did it cost". I am not yet prepared to tell ANYONE what
the total package cost; I don't even want to know myself. I will say
that if you really want or need a 150/150 you will be a LOT better off, both economically
and time wise, to sell your current plane and buy a flying converted
There is a lot of interest in the Flint auxiliary fuel
tanks.. To safely and conveniently fly the trips
that are normal for me more than 22.5 gallons of
fuel is needed. The Flint
tanks, that add an additional 23 gallons of useful
fuel and 35 pounds
of empty weight. They are installed in the outboard portion of the
wing. The last rib has a hole cut into it and the tank slides into the
wing. A fuel pump is installed between each aux tank and main tank and when
needed fuel is pumped down from the aux to the main. I fly until I have
burned 12 gallons
of fuel, then pump fuel from the aux tanks until the fuel gages on the main
tanks read full. When I have burned 24 gallons I pump
the fuel remaining in the aux tanks into the mains.
The Flint tanks are well made, the
documentation is excellent and the support is outstanding. However, the
resulting fuel system is much more complicated that is commensurate with a
150. If they can be found the stock Cessna long range tanks (patroller
tanks) even at only 40
gallons are a simpler and better choice.
holds an STC on converting standard tanks from 22.5 to 40 gallons.
I really feel that this is a better solution. The installed cost of
the long range tanks are about the same as the auxiliary tanks but maintain
the simplicity of the original Cessna 150 fuel system.
To assist in fuel management I installed
a JPI FS450 fuel flow computer. I have flown with a fuel flow
computer for many years and given the inaccuracy of stock fuel gages it
gives me a good deal of comfort to have a cross check on my fuel burn. I
have found the readings of the flow computer agree within +/- 0.5 gallons with
the fuel truck meter.
Since there is no manual information on
power settings for the prop, engine, airframe configuration I use the flow
meter as my primary means of adjusting power. The Lycoming owner manual
provides a set of curves for fuel flow at various power settings. 75% =
8.4GPH 65% = 7.3 GPH 55% = 6.2 GPH I don't pay much attention to the
Tachometer, I just let it run what it takes
to get the specified fuel flow. As I climb the tach
reading heads on up toward the red line. Talking to Jeff and Chris I find
that I burn more fuel than they do and that is due to the fact that they
don't flog their engines as hard as I do.
I installed a four point Alcor EGT to assist in accurate leaning. I don't feel
that the cost and complexity of a four cylinder engine analyzer is
justified for the low compression, normally aspirated 0-320. I lean to 50° rich
of peak for best economy, per the recommendations in the Lycoming owner's
manual. I found that the "lean until the engine runs rough
the enrich the mixture a bit works just a well as
the EGT. If you just have to have another gage in the panel make it a
four place CHT; if you take care of your cylinders they will take care of
I installed a King KFC200, two Icom A200 com units, a Narco 122 nav radio
(VOR/ILS), a Sigtronics two place intercom
and rounded it out with a S-Tec Model 40 coupled auto pilot. I kept
the Narco AT 150 transponder
that was in the plane. My primary navigation chores are accomplished
using a Garmin CPSMap 295 GPS. I had the radio
system and static system tested and certified for IFR flight for those
occasions that it may be necessary to go IFR for safety.
It has long been my personal policy not
to fly single pilot IFR without at least a minimal auto pilot. The S-Tech
Model 40 coupled to the VOR and a DG with heading bug serves nicely to
assist in maintaining heading during long trips or in IFR conditions.
It is also a big help on long trips.
All in all I am very pleased with the
package that I call the Sport Hawk. My trip to and from Clinton last week
was my first really long cross country trip in the plane and I very pleased
with the results. With favorable winds a 1000 mile trip is
easily accomplished in a day, it took me 7:30 and one fuel stop to fly the 943 miles to Clinton. When the
winds are against me I think that 700 miles would be more comfortable, the
return trip took 9:30 with two fuel stops and I was pretty tired when I got
Would I recommend a 150/150. I surely would. The performance is pretty
spectacular and it is the most fun I have had flying in a long time.
However, if you are flying in low country and don't require strong climb
and high altitude performance a stock 150/152 is just dandy and a lot
As with most things in life the 150/150
entails some compromises. For strong climb and a little increase in speed
you must pay with flying a heavier airplane; forget 1600 pounds and be
prepared to take off and fly most of the time at above certified gross
weight. You also pay in increased fuel consumption. Sure you can pull back
to 50% power and burn about the same rate as a stock 150 but I'll bet that
Would I build another 150/150? No way.
You can buy a flying airplane for a LOT
less than you will have tied up in converting your own plane. It took
nearly eight months and a bunch of buck to get the Sport Hawk flying.
I hope that the foregoing answers
questions that you may have about 150/150 conversions. Please bear in mind
that these are my opinions and you may get a completely different slant
from some other 150/150 owner.