Fixed Pitch Diamond Star
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Linda Armstrong practicing her navigating en route to North Bay
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Hot, humid, hazy. The Garmin 1000 is a God send for navigation. |
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Flying over Kirkland Lake |
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Carol and Ron Cook and sister Carol at North Bay |
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The flight crew with refueller in North Bay |
Some pilots reckon aircraft improvements leap ahead with increased thrust. They believe that more power is beneficial at any cost. Those folks can read elsewhere today.
Aviators who consider initial purchase price, insurance premiums, and overhaul costs as major factors in aircraft ownership should consider the fixed pitch, carbureted Diamond Star.
This recent addition to the very successful Diamond Star line targets the low cost end of the four place market and aims to provide superior performance compared to their competitors while minimizing the entry level price.
Diamond Aircraft granted my request to borrow their demonstrator for a seven hour cross country flight evaluation from London, Ontario to Kirkland Lake and return on family business.
My sister, wife and I when combined with full fuel (240 lbs.) and the 66 pound baggage compartment maximum brought the take off gross weight up to the maximum of 2,535 pounds.
We all tip the scales on the plus side of TCA specified occupant weights, as is common nowadays. The result - we added up to 560 pounds.
Externally, the Stars look alike. The constant speed (C/S), injected version produces enhanced efficiency with its induction system and the propeller produces more thrust and increased performance.
However, C/S and injection systems when combined really balloon the bottom line purchase price, weight and overhaul costs. There are many pros and cons between these systems; however, in the case of the Diamond Star FP, the major benefit is price.
What’s she look like?
She’s a fantastic plastic with long slim lines and her attractive features drew spectators everywhere we landed. The cabin is spacious for four and the large window areas provide excellent views for all. The seats are firm, the kind that provide good support for lengthy cross country flights and the rudder pedals slide fore and after to accommodate short and tall aviators.
There are no seat adjustments so it is prudent for prospective purchasers to set a spell in the cockpit and rear seats to ensure their physiology fits the aircraft’s
We stopped at North Bay to visit retired COPA director Ron Cook and his wife Carol. They use seat cushions to fly their Cub floatplane and would have to do so in the Diamond Star to see over the high anti-glare shield.
Almost all purchasers opt for the exotic Garmin 1000 dual flat screens and the mandatory round back up instruments mounted above result in a large panel.
Since most of the weather on the four segment trip was in marginal VFR I found the full panel and large moving map display exceedingly useful. The weather was hot, humid and hazy with flight visibility averaging 5 miles.
The return trip featured 35 knot headwinds and the attendant mechanical turbulence these climactic conditions produce on the Precambrian Shield of northern Ontario. The Humidex threatened 40 and surface temperatures hovered around 32 Centigrade giving airport DA’s hovering around 3,000 feet.
Not optimum flying conditions; however, the negative effects were minimized with the Diamand Star’s comfy cockpit and desirable design.
My new mistress is the Garmin 1000 and her presence made the flight conditions enjoyable as I was generally too busy enjoying all she offers to pay much attention to the climatology.
Standard fuel is 40 U.S. gallons in two selectable wing tanks. Both have vents and drains and a third gascolator drain is located behind the engine in the engine cowl opening to drain the lowest point in the system. Optional long range tanks are available which increase fuel capacity to 51 U.S. gallons.
Electronic flight instrumentation to make airline pilots desirous
Click the Bat/Alt switches on and the panel lights up with an EFIS magic show. If you thought the 430 and 530 Garmins were wonderful, you will be astounded by the 1000 series.
I am generally opposed to equipment that challenges pilots with horrendous numbers of “bells and whistles” that subsequently have the potential to overwhelm our memory capabilities. While this package provides copious quantities of data, they are all readily accessible and entirely useful data to pilots.
The scope of this article (or a series for that matter) is insufficient to detail the electronics capabilities. Suffice to say, the Garmin 1000 will likely be the best GPS/Nav/Com package you will have flown with and it offers full engine monitoring as well. Frankly, I would rather have the Garmin colour presentation available on the Diamond than the three tube B&W displays on our CF-18 fighters.
Danger and cautionary warning displays are always surreptitiously monitoring important parameters to immediately provide data on any system that is about to exceed limits. Moreover, the screens are so large that room exists to have combinations of the nearest airports’ data, conflicting air traffic, weather and other significant data displayed at the same time.
Prospective purchasers should check the availability of traffic avoidance and uplinked weather capabilities in their planned operating areas since NavCan has not yet provided these services to its Canadian users.
While some airliners are flying with equivalent equipment, most of the world’s airline captains aren’t as lucky as Diamond Star owners with Garmin 1000 displays and a few friends and acquaintances flying heavy metal have drooled on these offerings.
Truth to tell, this scribe invested many hours with the manual to enable me to fully utilize this powerful series of tools. When I climbed into the bird and applied 24 volts to the system, my mind went blank – similar to some folks being flummoxed on sitting down to a final exam.
Still, having worked with other GPS’s as I climb from cockpit to cockpit, I intuitively worked my way though the knobs, dials and switches and was able to untilize 30-40 per cent of the capabilities by the time the oil was up to temperature and the throttle full forward.
Playing with the Garmin en route helped disclose more and more of it powerful capabilities. The multi page quick reference guide really helped with my education en route. I looked forward to an upcoming 15 hour cross country in a Diamond Star to hone those skills and knowledge; however, at the last moment, the Seattle dealer sent two instructors to pick up the plane.
Slip inside and enjoy her ride
Although a carburetted Lycoming is installed, an electrical priming pump is utilized to provide easy priming and starting with a slightly open throttle (Years ago I learned that many aircraft with hand plunger primers leak fuel after engine start up and this results in an overly rich cylinder and carbon deposits).
The aircraft can be moved before the GPS and other electronics are fully “locked on” as the system searches while taxiing towards the active. This was good because the cockpit was “cooking” in this oppressive heat and humidity.
We alleviated the climate’s effects by propping open the front hinging canopy with the CFS (not much use for anything else as the Garmin database provides the useful information at the touch of a button). This provided substantial airflow in the cabin – at least as much as I’ve felt in any airplane – including open cockpit biplanes.
Steering is by swivelling nose wheel and differential brakes. While this requires occasional taps of the brakes for taxiing, it permits very tight manoeuvring with the fully castering capability.
Directional control was good, even in the strong cross winds experienced in the runway environment throughout the trip.
Run-up is typical of the Lycoming O-360 series and take off flap is selected by moving the lever to the first position.
Gross weight acceleration is steady and we look for at least 2,200 rpm static at the start of the roll. Even though this would indicate a propeller optimized for cruising speed, the DA 40 FP breaks ground repeatedly in 900 feet at 60 knots and accelerates quickly to the 70 KIAS best rate of climb speed. Even in the hot weather at gross weight the needle hovered around 1,000 fpm in the turbulent air.
At a safe altitude of approximately 300 feet the flaps were retracted followed by a few seconds of “sag.” With the fixed pitch prop, I was inclined to let her accelerate to 100 KIAS for better visibility and cooling in the climb and ROC averaged 500-600 fpm to 6,500 feet.
The controls are very light and responsive and I found I was over controlling a little in roll in the marginal visibility and quickly learned to leave the plane trimmed and not keep placing minor amounts of input repeatedly into the stick.
I reckon the stiffer controls of my motor glider in cruise have “heavied up” my inputs and I was somewhat “rudder happy” when none was needed.
Other than in the climb, when some right rudder is necessary to “center the ball” the plane can be flown feet on the floor – and should be (Incidentally, there is no needle and ball as that data is depicted in the flight display symbollogy).
Whether cruise climbing or opting for steep obstacle clearing climb-outs, temperatures stayed well within the green. Allowing the engine to “wind up” to 2,650 rpm yielded a mixture rich cruise-climb fuel flow of approximately 15-16 U.S. gph.
Levelling out between 4,500- 8,500 feet and setting 2,450 rpm resulted in fuel flows of 8.4 - 10.1 gph with the lower flow and higher true airspeeds being found at higher altitude.
There was lots of expansive window area to observe the haze restricted visibility and it was easier to fly on instruments than try to see meaningful distant checkpoints through the mung.
Without an autopilot and with my devoting most of my time to learning the secrets of the EFIS, I was delighted the machine flew stable and was a better platform when I wasn’t fiddling with the controls – although it took me an hour to realize this.
It didn’t help that the demonstrator hadn’t been completely rigged yet so the left wing was heavy until I shifted the rear seat passenger and ran on the left tank for an hour - then she became a hands off plane.
The cruise power setting resulted in a 122 KTAS cruise at gross weight and like an airliner, after 2.5 hours of fuel burn, she accelerated to 128 KTAS. On one long leg into a 35 knot headwind we got down to 1/3 fuel before descending after 3.5 hours on track and the TAS crept up on 133 knots.
On the topic of airspeed, the Garmin shows indicated A/S, true A/S, ground speed and a wind arrow showing the direction and exact speed of the wind. This data really helps select a cruising altitude to enhance efficiency whether it be miles per gallon or minimum en route time. This amount of data can allow a savvy pilot to save fuel and beat faster aircraft over the same route.
On the return trip into the strong winds we were generally kept quite low by convective cloud and had to live with light to moderate turbulence. It’s difficult to quantify something like this, but after having flown hundreds of aircraft types in turbulence, I sense the Diamond Star handled the bumps and grind quite well. Disturbances pitched and toppled the aircraft around somewhat but it displayed a strong tendency to return to level flight. Moreover, the light controls made it easy to level the wings and pitch attitude on the occasions it was desirable.
My sister has flown little in light aircraft and my wife dislikes turbulence; however, neither had any trouble with comfort during the flight.
We used my two passive headsets up front and my sister wore none in the back. Nonetheless, the sound level was very low thanks to the naturally insulative layers of composite construction and we had no trouble engaging in conversation in that environment. Some of the time we simply used the speaker to monitor radios and this really reduces the discomfort of wearing the headsets with their high clamping pressure in those ambient conditions.
Ventilation was superior in the back seat in-flight, but I would have enjoyed more airflow up front as it was quite warm even at altitude with an OAT of 12 C. The sun on us front seat occupants and only one vent each to aim at part of one’s body left me wanting more airflow.
As reported in previous articles, the slow flight and stall characteristics of this series are benign with no sudden, unwarranted tendencies. Flight speeds approaching the yellow line in turbulence were also easily controlled. The airplane is slick but not slippery.
In the runway environment, speed control and touchdowns with no flap, T/O flap or landing flap are easy, smooth landings are readily repeated. Our last landing in London had winds directly between the main runways gusting at 18-30 knots. This put the wind squarely down Alpha taxiway and on the 20 knot cross wind limit for the aircraft. I asked the tower controller if he would essentially condone a landing on the taxiway (something I did frequently on military bases during paradrop operations) however he declined.
Notwithstanding the amount of cross wind, our one wheel landing was the smoothest of all of the good landings provided by this bird – probably because I was paying more attention. She sashayed like a lady in the buffeting winds all the way back to the tie down area and as we exited the aircraft in an area that provided a venturi to the winds, she tried to turn into the wind before we could tie her down.
The fact that the Diamond Star was so docile during the landing and taxiing in that blow says a lot about her ability to operate from runway environments that are plagued by cross winds i.e. landing areas which don’t have three crossing runways.
Incidentally, during my second cross wind landing in North Bay, I elected to make a steep approach with only take off flap selected due to the winds. Side-slipping on final showed a strong rudder and the ability to neutralize crosswinds with large sideslip angles.
Strangely enough, the only other light aircraft to land in the London cross winds was the Diamond Twin Star demonstrator with Diamond employees Jeff Owen and Walter Slingerland returning from demonstrations in Connecticut. Kinda says something about fleet handling – doesn’t it?
Composite conclusions
The first airplane I owned that fit this category was my shiny new 1975 Cessna 172, CF-KLA (still looking new after rebuilds and flying out of Ottawa) with a list price of $25,000 Although the known aerodynamics data from those days is little changed today other than prices.
Aircraft builders have been refining their production techniques to tweak small performance improvements over the decades. Many of the performance enhancements evolve from composite construction and this area will continue to improve due to the ability of these fuselages to take on complex curves to optimize space inside and streamlining outside.
Handling characteristics, control response and stability also eke out continuing gains through trial and error and production capabilities and robotics that were unheard of decades ago.
New aircraft are built to higher tolerances and this also steps up performance. Quite frankly, other than improved ventilation for this summer climate, there is nothing I could suggest to improve this entry level four place.
Notes on data charts
Due to the inherent theme of my conclusions, I have chosen the Garmin 1000 equipped “New” Cessna 172 for comparison purposes to place the competitors in a mutual perspective. It should be noted, it’s difficult to actually compare these two aircraft in terms of price as the standard and optional equipment lists are quite different between them and it should be noted that data provided is generally from company brochures.
Moreover, there is not a great deal of performance differential between the two aircraft as they trade-off the lead on various parameters. A purchasing decision may come down to a preference between high and low wing aircraft.
As a result, I have included third party information showing relative efficiency data between a series of aircraft. Personally, as an efficiency freak, I find this sort of comparative data very useful. Please note that the Diamond Star used in the third party fuel/range graphs is the constant speed version.
Ken is a director on the COPA Board. He lives in Victoria, B.C. and provides services internationally in advanced training, expert witness, flight test and aircraft sales. He has logged more than 15,000 hours on 375 types of fixed wing and rotary aircraft. Soaring his Diamond Xtreme is what he does for pleasure.
Fixed Pitch Diamond Star Cessna 172
Power (H.P) 180 180
75% Cruise 125+ 124
Range (nm) 504 518
Stall (full flaps) KIAS 49 48
Runway performance at SL, gross weight, applicable flaps in feet
T/O Distance over 50’ 1814 (POH) 1630
LDG Distance over 50’ 1518 (POH) 1335
Standard Fuel USG 40 usg 53 usg
Cabin Width 45” 39.5”
Height 6’ 6” 8’ 11”
Length 26’ 3” 27’ 2”
Wing Span 39’ 4” 36’ 1”
Empty Weight 1620 1644
Gross Weight 2535 2550
Useful Load 915 895
T/O ROC (fpm) 920 730
Fuel flow and range calculations
NO WIND
Aircraft Speed (kt) 400 nm time 400 nm fuel (gal) nm/gal
Beech Bonanza 35 160 2:30 35 11.4
Beech Baron 55 (twin) 188 2:08 58 6.9
Cessna 172M 120 3:20 27 15.0
Cessna 182 140 2:52 39 10.4
Cirrus SR-22 180 2:13 36 11.0
Diamond Star 147 2:43 25 16.2
Diamond TwinStar (twin) 181 2:13 24 16.9
Mooney 201 160 2:30 26 15.2
Piper Warrior II 127 3:09 27 14.9
Piper Arrow 137 2:55 31 13.1
Piper Seneca (twin) 197 2:02 59 6.8
20 KT HEADWIND
Aircraft Speed (kt) 400 nm time 400 nm fuel (gal) nm/gal
Beech Bonanza 35 140 2:52 40 10.0
Beech Baron 55 (twin) 168 2:23 65 6.2
Cessna 172M 100 4:00 32 12.5
Cessna 182 120 3:20 45 8.9
Cirrus SR-22 160 2:30 41 9.8
Diamond Star 127 3:09 29 14.0
Diamond TwinStar (twin) 161 2:29 27 15.1
Mooney 201 140 2:52 30 13.3
Piper Warrior II 107 3:45 32 12.6
Piper Arrow 117 3:25 36 11.4
Piper Seneca (twin) 177 2:16 66 6.1
20 KNOT TAILWIND
Aircraft Speed (kt) 400 nm time 400 nm fuel (gal) nm/gal
Beech Bonanza 35 180 2:13 31 12.9
Beech Baron 55 (twin) 208 1:55 53 7.6
Cessna 172M 140 2:52 23 17.5
Cessna 182 160 2:30 34 11.9
Cirrus SR-22 200 2:00 33 12.2
Diamond Star 167 2:24 22 18.4
Diamond TwinStar (twin) 201 1:59 22 18.4
Mooney 201 180 2:13 23 17.1
Piper Warrior II 147 2:43 23 17.3
Piper Arrow 157 2:33 27 15.0
Piper Seneca (twin) 217 1:50 54 7.5