Estimated reading time 16 minutes, 4 seconds.
On Aug. 11, Eagle Copters announced that it had received Federal Aviation Administration certification for its single-engine conversion of the Bell 212, the Eagle Single. In this story from the Vertical archives, Shawn Coyle flight tests the Eagle Single and reports on its capabilities.
The Eagle Single is a unique bit of reverse engineering andaircraft restoration, it begins life as a used twin-engine Bell 212, but istransformed into a new single-engine hauler.
There has to be a very good reason why any company sets outto make a major engineering change to an existing and proven aircraft. One ofthe main reasons is identifying a window of opportunity to provide somethingthe market wants and needs.
While Eagle Copters of Calgary, Alta., is no different inrecognizing and trying to fulfill an identified need, its decision to take atwin-engine helicopter and make it into a single-engine ship is quite thereverse of what many would expect. The new Eagle Single is based on the Bell212, which has been around since nearly the dawn of helicopter time, and isitself a twin-engine version of the Bell 205/UH-1H. To change this venerablemodel back to its single-engine roots appears to be a step backward to some,but is in reality a very clever move.
A Need Fulfilled
The Eagle Single design began with the understanding thatthere was a deep and abiding need for a utility helicopter that operates in themore austere places of the world (i.e., in the backwoods), where payload isking. Payload, after all, pays the bills.
The Bell 212 was (and still is) a very good utilityhelicopter, but there are many missions where the second engine is not needed.If you take that and the combining gearbox out, you not only save weight, yougain extra carrying capability. Replace the remaining engine with one that willmatch the increased horsepower capability of the transmission, and you’ve got amachine that is easier to operate and much less complex. That, and more, isprecisely what Eagle has done.
To get a closer look, the Vertical team joined up with DayAviation in Sudbury, Ont., on a beautiful May morning to test fly its newlycertified Single. John Van Zon, Day’s chief pilot and maintenance manager, gaveus a complete rundown on the changes made to transform the 212 into the EagleSingle. And, while Day’s Single looked brand new, it actually had over 20,000hours on it from its previous life in the Gulf of Mexico. This showed that notonly had Eagle had done a wonderful job on the engine and associated changes,but in restoring the entire machine.
From the outside, if you ignore the engine cowling, theSingle is a 212. When you look inward, though, you’ll start to see the changes. The fuel system remains pretty much the same, butthe fuel tank interconnect is now permanently open. The electrics are simpler,with only one generator and no inverters. That single generator, though, meansno instrument flight rules. For the missions the Single would normally fly, this is not a problem.
That new engine in Day’s Single, meanwhile, is the latestversion of the venerable Honeywell T53, the -17BCV (on which Eagle andHoneywell have teamed for distribution, see p.21, Vertical, April-May 2008).We’re not just talking about the same engine that evolved in the Vietnam War -this is a re-engineered model with significant changes to the rotatingcomponents to improve their durability and reliability. While the non-rotatingcomponents and the outside may look similar, like the ship it powers, it’s theinner workings that make all the difference. All this leads to an engine with1,800 shaft horsepower at sea level, standard day, uninstalled conditions, witha 5,000-hour time between overhaul, which, if nothing else, is a good enoughreason to change from two engines to one!
The skids on the Single we flew were Dart HelicopterServices’ moderate-height version, which made the climb to the cockpit slightlylonger than I was used to in the military version. Once in the cockpit, you’llimmediately notice the main difference in the cabin – the electronic displaysand much simpler overhead and center consoles. The electronic displays were thelatest from Sagem, and had just received their final Transport Canada blessingonly two days before we flew the ship. They were very clear and easy to read,with one exception (more on that later).
Familiar and New
Start-up was very straightforward – the ship only has oneengine, after all. This is when things started to feel very familiar again,which meant mostly good things. The one minor criticism I had, though, carriesover from the 212, and concerns the electro-mechanical idle release. Therelease needs electrical power to shut the throttle off. The problem is that ifthe battery or ground power dies with the throttle above the stop, you can’tshut the engine off. Generations of pilots have learned to put the throttlejust below the stop until after the engine has started successfully. Why thishasn’t been changed to a purely mechanical stop is a continuing mystery.
That minor problem aside (hey, I’m allowed to get grumpy inmy old age, aren’t I?), this was just like the 212 I knew and (mostly) loved.Systems checks were simpler, though, and the electrical system was a non-event.Soon, we were ready to do the photo shoot. As Van Zon flew initially, I watchedthe new electronic displays. The change from percentage torque to pounds persquare inch took a bit of getting used to, but if you were a Bell 205 pilot, itwould be like home.
Everything else was a trip full of nostalgia: noise andvibration were identical; the controls felt the same; and the effect of havinga lot of power to use was just the same. Even when picking up a full BambiBucket, torque was hardly into the takeoff region, and the cool temperaturesand low-pressure altitude we were in meant we were so far from any enginelimitations that I didn’t even comment on them.
Van Zon, though, commented on the fuel burn. Day was used to600+ pounds an hour on the 212, and now the company was seeing around 550 andoften less. Given that the two PT6s on the 212 were both operating at wellbelow their maximum power all the time, the fact that their specific fuelconsumption (pounds per horsepower per hour) or fuel efficiency would be worsethan one T53 working closer to it’s maximum power, makes sense.
Well Thought Out
Using the electronic displays was straightforward, and wasjust a matter of learning where to look for the right gauge for any of thelimitations. For the more advanced stuff like setting the altimeter, all ittook was pushing the appropriate line-select key on the right-hand side of thedisplay and using the “master” adjust knob at the top of the row of buttons onthe outside of the center console, one for each side. Some functions, such as altimeteradjust, had a dedicated knob, but the most convenient method was to choose theappropriate line-select key then adjust the numbers. Of course, normal featureslike “press to center” were incorporated for heading and course selections.Getting used to these displays would take minutes, but I imagine reallyextracting the most from their awesome array of features would take a bit oftraining.
The only gripe I had about the displays was the electroniclegends. As clean and crisp as the displays were in nearly all places, I haddifficulty reading the small print on the electronic legends beside theright-hand line-select keys. Dark green letters on a light green backgroundwere a bit indistinct for these aging eyes. It seems the extra space next to theboxes could be used to make the fonts a smidgen larger, and a change in thecolor scheme to have more contrast between text and background would also helpsolve the problem. Of course, a pilot who spent any amount of time with thesystem would quickly know what each label said, so this may be the test pilotgene in me leaking out again.
Other minor features in the Single abound. For one, the chinbubble window is now viewable. This is because the instrument panel is slightlyshorter than the one in the 212, so there is a large cutout under the maindisplay, on both sides, in front of the pilot.
One of the slightly surprising aspects found on a quick passthrough the flight manual is the nine-passenger limit. Why only ninepassengers? This limit will actually help the operator, as it lets theheight/velocity curve reside in the performance section, as opposed to thelimitations section of the flight manual. It’s a minor point, but a veryimportant legal one.
Looking over Day’s Eagle Single with a critical eye, it wasimpossible to tell this was not a brand new airframe – there was not a wrinklein the skin, not a bubble on the paint. There were no signs of aging at all.There was not even any deeply ingrained soot on the tailboom. I couldn’t evensee evidence of just being painted over. This ship was not just cleaned up, itwas made new again. Given the data plate said the airframe started life in 1977, I began wishing someone could make me look like I did back then
All in all, the Eagle Single is an impressive piece of bothengineering and workmanship. The engineering to take a twin-engine helicopter,simplify it, and improve the payload and fuel efficiency shows a keen eye forfulfilling the needs of a specific niche. As for the workmanship, I know of no wordsto say how nice a job Eagle did in making a 31-year old ship seem like new.
Special thanks to Day Aviation for allowing Vertical toflight test its new Eagle Single.
Shawn Coyle began helicopter life in the Canadian Air Force,and was fortunate enough to attend Empire Test Pilot School. This started anon-stop flight testing career, including teaching at three test pilot schoolsand working for Transport Canada as an engineering test pilot. Shawn iscurrently developing helicopter simulators and teaching seminars on helicopterflying.
Making the Single
By Gary Watson
The Eagle Single, the latest offering focused on rejuvenating Bell mediums, is currently a hot topic of conversation among pilots, owners and customers alike. Pilots appear to be very partial to the additional lifting capability. Owners like the cost of operation. And, customers like the additional option of contracting a helicopter that most of their employees are familiar with.
This is all great, but what about the folks that must keep this hybrid, 40-year-old design serviceable on a day-to-day basis? Is the Single just a simple engine reconfiguration ?to get more lift? Or has the blending of two aircraft?types (212 and 205) resulted in something that is difficult to maintain?
The answer lies in the process that morphs a Bell 212 into an Eagle Single. Fortunately for the engineer/mechanic, Vertical has learned that the modifications use the best features of both airframes.
The modification process starts when Eagle Copters’ aircraft maintenance engineers disassemble the airframe completely, stripping out all the wiring and removing all the mechanical components. Everything that’s left is bead blasted to remove paint and reveal corrosion. All control parts, bell cranks and push rods are cleaned, inspected and repainted. Any part that is corroded, worn or damaged is replaced.
Once the airframe is stripped, cleaned and repaired, it is ready to be modified to hold the new engine-transmission package. The Eagle Single modification replaces some B212 structural elements with B205 items, which facilitates the installation of the Honeywell T53 engine (a choice of -17A, -17B or the newest option -17BCV). Once the fuselage modifications are completed, the fuselage is painted. From this point on, the ship starts looking like a brand new helicopter.
The removal of 50 percent of the engines and the complex combining gearbox is obviously an improvement in the number of items for the engineer/mechanic to maintain. But, the engine and powertrain modifications also enabled Eagle to make the Single more maintenance-friendly.
A DART Aerospace driveshaft tunnel improves both access to the tail rotor driveshaft and provides more room in the engine/transmission deck area. The new powertrain takes up less space, so, unlike the B212, no components are protruding into the side walls in the rear of the cabin. Said Mike Mallon, Eagle’s director of maintenance: “We have left the upper web panels from the B212 in place beside the transmission to provide additional access into that area. We are also planning to add an additional access panel to the DART tunnel. The 205 engine cowlings have been redesigned and improved from the original B212 versions, so they are easier to remove.”
Eagle has modernized many of the accessory systems, improved access and totally replaced some of the?”crankier,” high-maintenance instrumentation with?modern, reliable, and, most importantly, easily sourced ?new components.
“Some of the instruments on the 212 and 205 are getting so old and unreliable that we often receive them back from overhaul and they do not work for any length of time,” stated Mallon. “We intend to replace many of these AC-powered instruments with new, high-reliability DC-powered ones that are very low maintenance items.” Some of the instruments that will be replaced will have new DC transducers and a combined analog/digital display.
Other gauges and indicators have already undergone modernization. Typical of the new technology instrumentation is the new main gas temperature indicator used with the T53-17 engine, which replaces the original ITT gauge. It is a combination analog and digital display, and is self-compensating. As such, it requires fewer calibration steps during installation or replacement. A new torque gauge, meanwhile, reads in percent rather than pounds per square inch. This means the plastic overlay showing operating ranges is no longer required. Most of the Single’s gauges are also equipped with internal lighting, so the need for post lights is greatly reduced.
The Eagle Single still uses the original fuel-quantity sensing system, but many of the small co-axial fittings that would often become intermittent have been replaced with permanent, matrix terminal block strips. Future plans for the Single could include a totally new fuel-quantity indicating system.
The current updates also encompassed the model’s wiring. Aircraft and panels are totally rewired, replacing the old, bulky wiring with the latest standards. To allow for easy removal as necessary, Eagle installs a number of quick-disconnect connectors on items such as the overhead electrical panel. The existing DC electrical control system has remained, but some components have been replaced and Eagle plans to replace the entire DC control system.
The avionics installation is based on the customer’s request and budget. Various Singles are operating with installations ranging from the basics, to full Sagem ICDS (as installed by Vector Helicopter Services). Most of the new equipment is very vibration resistant, and failures should occur with far less frequency than systems installed over the previous decades. The Sagem displays also provide all engine instrumentation and flight instruments, creating a very clean-looking panel with multiple viewing options.
The overall result of all these modifications and upgrades, which Eagle makes to create each new Single, appears to be a helicopter that requires less frequent maintenance. And, if a snag does occur, the replacement parts will at least be much easier to obtain.