Pilot report - Piper Aztec
[Reprinted from Fliteguide / Imperial Aviation]
Those who take an interest in light aircraft history will know that the industry
was formed by a collection of perverse and idiosyncratic characters. Each one
was to stamp their personal ethos onto the aircraft we fly today. Walter and
Olive Beech were just as comfortable with the cut and thrust of post-depression
business as they were mixing it with high society. When Walter died in 1950,
the slim, attractive and astute Olive took over the company's helm to steer
it successfully into the booming sixties and seventies. Dwane Cessna, who had
studied aeronautical engineering at Wichita University, reactivated his uncle
Clyde's aircraft factory in 1934. He then gave the company a strong engineering
core by employing two of his class mates; Tom Salter and Jerry Gerteis who became
largely responsible for Cessna's wide and diverse range of light planes. It
was this engineering strength that led Cessna into developing structurally innovative
aeroplanes, in particular the 337 Skymaster, and cantilever wing 210.
Piper was led by the unprepossessing and homespun 'W.T.' Piper who happened
to produce five sons, one of whom, Howard, was to be responsible for moving
a reluctant company into the modern age. If it had not been for Howard 'Pug'
Piper, the company would probably have died producing antiquated Cubs and Tri-Pacers.
It was Howard who recognized the huge advances made in all metal construction
methods by the end World War Two. With a wary eye on the celebrated 'V-tail'
Bonanza, Pug could not persuade his old man to develop the company's four-seat
PA-6 Sky Sedan beyond two prototypes and the project was cancelled in 1947.
Pug's next opportunity to drag the company away from tube and fabric aircraft
came in the early fifties when it became clear that a more sophisticated market
was demanding business aircraft - preferably with two engine safety.
Piper's conservative engineering standards came from WT Piper's disinterest
in the subject. Pug too was not an engineer but he was a great conceptual thinker
and doer. Moreover, the company, unlike Beech and Cessna, had no previous experience
in building twins. In fact Piper thought it a good idea to buy in a design,
especially as Beech had just launched their Model-50 Twin Bonanza. If WT was
a reluctant engineer, he was extremely adept with figures and quickly realized
that his bought-in design would be too expensive to produce for the customers
he had in mind. The company resolved to begin with a clean sheet design and
in 1952 flew their prototype model 23-01 Apache. It was to be the first of Piper's
Indians.
By industry standards, the Apache was not a technological leap. The fuselage
was constructed of steel tubing and initially covered with fabric. It also had
twin fins similar to those on the Beech 18. High single-engine rudder forces
quickly forced a change to a single vertical stabiliser taken straight from
the cancelled Sky Sedan. Despite a dealer network that was reluctant to sell
a Piper for so much money, the Apache was launched in 1953, selling for an unprecedented
(for Piper) US$32,500. The aircraft began to sell immediately, especially as
Cessna's 310 cost US$17,000 more and the Twin Bonanza a huge US$38,000 more.
In fact, Piper struggled to keep up with demand. Although the Apache was a great
deal slower than a 310, it did benefit from extremely benign handling and quickly
established a reputation for safety Thus, when customers began to clamour for
more power, speed and payload, the Apache's replacement, the Aztec, proved just
as popular.
So successful was the Apache that Piper's basic design was almost entirely carried
over to the new twin and early examples are difficult to identify from a distance.
The most noticeable change was the modestly swept back vertical stabiliser,
larger fuselage and longer engine nacelles which housed a pair of 250 horsepower
IO-540 six-cylinder Lycomings. Piper continued marketing the Apache which in
1962 adopted the Aztec airframe but used a pair of 235 horsepower O-540 Lycomings.
The Apache was finally dropped in 1965.
First Aztec deliveries took place in 1959. These early models shared the Apache's
short nose but its bigger fuselage carried space for six occupants and the larger
engines boosted speed to 205 mph in the cruise. A number of variants followed
beginning with long-nose B models in 1961 and it was in this shape that Aztec
production finally came to an end with the F model in 1981. From the 1964 model
C, turbocharging was offered.
Flying the Aztec
Although production had only stopped less than a decade earlier, by the late
eighties, Aztec's were already considered old and expensive and were often to
be found derelict around various Gauteng airfields. Many South African aircraft
had led tough lives as charter aircraft and by the time their useful life had
expired, some were to be found providing a seemingly cheap step into the heady
realms of multi-engine flying. Pristine examples were rare and many of the aircraft
still flying were showing signs of their age. It was in one of the latter aircraft
that I completed my multi-engine rating and whoever owns ZS-MBG nowadays is
welcome to call me - I have some interesting tales to tell, especially concerning
an adventurous holiday to Malawi which tested the very limits of my patience
and ingenuity.
I will never forget staring at the decrepit innards of the valve technology
avionics scattered across the bench of Air Malawi's radio repair shop! So it
was with great affection that I settled into Daniel Coetzer's pristine E-model
Aztec, ZS-OFR, which he had rescued from almost certain dereliction after a
hard life as a Kenyan charter hack. Like many Aztecs, Daniel's aircraft was
bought cheap and has had a great deal of care lavished on the engines, airframe
and interior to bring the aircraft back to its former glory. Both OFR's hefty
Lycoming engines were fresh out of a top quality Alton Engineering overhaul
with less than ten hours running time on them. IO-540 overhauls are not cheap
but Daniel had spared no expense in having them worked on and even ordered a
full set of Millennium Cylinders. The IO-540 should be worthy of its 2000 hour
TBO and indeed the engine has a good record for easily reaching this limit.
However, over the years, with many engines on their second, third and sometimes
fourth overhaul, and often suffering on-condition component replacement, these
engines often need a top overhaul at midlife. Thus, Daniel approached his overhauls
with a clean-sheet wish to have the best available.
Being a perfectionist, it wasn't only the engines that received Daniel's attention.
OFR's interior was completely refurbished along with the panel. Sitting proudly
in the centre avionics stack is a shiny new Garmin 430 combined VHF and GPS.
The Aztec's panel was never a masterpiece of ergonomic purity and the Garmin
does clash somewhat with an ancient King Analogue ADF, a remote DME and various
other items which in the sixties were considered state of the art. However,
in Daniel's aircraft, all of it works including the Altimatic-5 autopilot and
a more modern King slaved HSI. There is further evidence of Piper's old hodge-podge
approach to panel design. The system switches are lined up on the lower left,
above the pilot's knees and the engine start buttons as well as magneto rocker
switches are attached to the left side of the cabin, this time just above the
pilot's left knee. The gauges are all lined up along the top of the right panel
in a way that manages to destroy any semblance of aesthetic symmetry. Below
the power lever quadrant is the flap and undercarriage lever with two cowl flap
levers in between - behind which sits the all important hydraulic power pack
driven by a pump on the left engine. The primary emergency pump lever snuggles
below. I'm not sure of Piper's thinking at the time but would hazard a guess
that this layout helped to create a flat floor making it easy for the pilot
to slide across to his seat. The most glaring omission is the absence of any
rudder or elevator trim controls. These are mounted horizontally on the roof
and until the early eighties remained a quaint if slightly illogical feature
of early Pipers.
Make no mistake; the Aztec's cabin is big. Early publicity photographs showed
be-hatted pilots beaming languidly from behind the panel. Settling in must be
like getting into your old family Chev during the sixties.
A tubular airframe is never easy to hide behind cabin trimming without having
a great deal of space between the interior trim and exterior aluminium skin.
The Aztec is typical of this as evidenced by the window sills and airframe tubing
that protrudes from the cabin roof into the top of the instrument panel.
The fuel selectors are located between the front seats and the system is simplicity
itself. There are two tanks per wing, though an optional long range system was
sometimes installed in the wing tips. OFR has standard tankage with a capacity
of 144 gallons. The entire contents are available for crossfeed in the event
of an engine shut down.
The two Lycomings start easily from cold with the left hand engine being started
first so that hydraulic power is available soonest. Pre-takeoff checks are entirely
conventional save for Piper's unusual recommendation that the mixture is not
leaned off below 5,000 feet. In most light aircraft, this procedure is carried
out above 3,000 feet. A glance at the two roof-mounted trim indicators is amongst
the last 'full-and-free' final checks before lining up on the runway. At this
point, a wise twin pilot will be thinking of the all important critical takeoff
speeds so that he is ready to make some fast decisions in the event of an engine
failure. Like the Apache, the Aztec is a kindly aircraft, but like all twins
requires decisive handling under asymmetric conditions. The aircraft responds
quickly to full power application and accelerates to its rotation speed with
a firm and reassuring push in the back. With a constant backpressure on the
control column the aircraft lifts off at just over 70 miles per hour and as
soon as an aborted takeoff is no longer an option the gear is retracted as well
as any flap. The minimum single engine speed is an extremely low 80 mph and
the Aztec accelerates quickly through this speed to its best two engine climb
speed of 120 mph (104 knots). With a maximum one-engine ceiling of 5,000 feet
at gross weight, any engine failure in this configuration is likely to result
in a downward trend at South Africa's inland airfields.
Some of my previous Aztec time involved some gross weight flights and I found
the aircraft to be weight sensitive in the cruise regime. This also affected
endurance but under normal circumstances an Aztec should return a consistent
160 knots in the cruise. Piper claim substantially more but in my experience
Piper's claimed speeds rarely match reality. Gross weight is 5200 lbs and empty
weight 3042 lbs leaving a maximum payload of 2158 lbs. The aircraft is thus
able to carry full fuel and fill the seats with a small baggage allowance for
each passenger - a great combination and a major reason behind the Aztec's tremendous
sales success. Indeed, the aircraft is truly versatile with huge luggage bays
behind the rear row of seats and inside the nose. Despite its respectable load
carrying ability, these vast caverns are an invitation to overload.conditions.
The big Piper twin also has a reputation for being a gas guzzler. This is hardly
surprising considering the two thirsty 230hp Lycomings. The operators manual
claims a cruise fuel consumption of 27 gallons per hour - enough for a tanks
dry endurance of five hours and giving a no reserve range of 940 nautical miles
- plenty to get from Johannesburg to Maun and almost all the way back again.
It's no wonder the aircraft was so popular with charter companies throughout
Africa.
The Aztec is pleasant to fly though few twins, with the exception of the Baron
could be described as having responsive handling. It is extremely unlikely that
Aztec owners will buy their aircraft with the object of performing mild aerobatics;
therefore any discussion regarding the finer points of handling is purely academic.
As an IFR platform, the aircraft is immensely stable though it does suffer from
the unusual characteristic of raising its nose with the application of flap
- a thing to remember on approach for unfamiliar pilots.
There is no better way of sampling an aeroplane's handling qualities whilst
flying formation. We were tasked to team up with a Cessna 172 - such a dissimilar
mix is nothing unusual in the magazine world of air-to-air photography. I found
the Aztec easy to hold and change position behind and too the right of the Cessna,
especially in a left bank as we circled over the busy flying area west of Pretoria.
A right turn where we were or the inside of the 172 and thus slower, encouraged
the beginnings of a buffet from the powerful elevator. The Aztec was gently
telling us that we were nibbling at the edge of its stall envelope. I rolled
out wings level and allowed the Cessna to continue its turn before rejoining.
This was an ideal demonstration of the Piper's gentle handling.
Returning to the circuit, I slowed to 150 mph on an early base to bring the
gear down - double checked by a handy mirror stuck to the inside left engine
cowling. Although many pilots might distrust these highly engineered hydraulic
power packs, especially if they have flown Cessna 210's, I've yet to hear of
an Aztec having to endure a wheels up landing following a system failure. As
a last resort though, Piper thought fir to install a secondary emergency system
which blows the wheels down with a blast of COČ. Much like a hand grenade, this
is activated by pulling a firing pin under the pilot's seat. First stage flap
can be lowered at under 160 mph but the speed needs to be below 125 mph for
full flap. As I lowered flap in stages during the approach it was slightly peculiar
to have to apply nose down trim. The aircraft is easy to land and requires no
funny control inputs at the flare - unlike the Aztec's earlier sister, the Apache.
Moreover there is little tendency to float if the speed isn't just right like
trying to place a Twin Comanche onto the runway. Lovely!
It was a profound pleasure to fly an Aztec once again and sample its kindly
flying qualities; especially one is such fine condition as Daniel's. Owning
one that isn't in top condition might be a more frustrating experience though.
Despite its obvious robustness, there are a number of items to look for when
appraising the Piper twin. I'm told that a fuel tank mod is required that involves
inserting a wedge between the rubber bladder and wing skin. The purpose of this
is to prevent fuel from collecting behind any folds or ridges in the tank thus
preventing all the fuel from feeding into the engines. This mod costs over US$1,000
to install. I can't imagine any sensible pilot allowing the fuel state to get
anywhere low enough to benefit from these wedges but regulations is regulations
I suppose. With so many Aztec's leading a hard charter existence in a previous
life it also pays to see if the step attach point has been beefed up. Piper
mandated a reinforcement as the attach point is mounted on the same piece of
tubular airframe as the rudder pulleys. The implication here is obvious. Lastly,
the flaps are relatively large and there is considerable strain on the flap
spars. An experienced Aztec engineer would look closely at this area as it is
not uncommon to find cracks.
The Aztec remains an intriguing choice for the used aircraft buyer. Whilst it
is fairly heavy on fuel, the initial purchase prices are usually low enough
to make up for this. These aircraft also allow a potential owner to source a
well used example and have it refurbished to a high standard for much less than
the cost of a Baron or late model Cessna 310.
Specification
Engines:
2 x Lycoming 250hp IO-540 C4B5. 2000 hr TBO
Propellors:
2 x Hartzell two-blade
Seats:
6
Wing span:
37.2 feet
Length:
31.2 feet
Height:
10.3 feet
Gross weight:
5200 lbs
Empty weight:
3042 lbs
Payload:
2158 lbs
Fuel capacity:
144 gallons
Fuel consumption:
Between 21 and 34 depending on cruise settings
Max speed:
210 mph (180 knots)
Max range:
1210 miles (long range cruise)
Takeoff distance:
820 feet
Min single eng control speed:
80 mph
Stall speed dirty:
70 mph
Ceiling:
21,000 feet
Single engine ceiling:
5,000 feet
[END OF REPORT]
Note: PlaneCheck often has some nice Piper Aztecs for sale