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Pilot
report - Piper Aztec
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 CO².
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
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1976 PA F -
23
250 AZTEC
