features A New Legacy

The venerable Bell 412 has learned some high-tech tricks from its younger brother, the Bell 429, and in doing so has gained a new lease on life.
Avatar for Guy R Maher By Guy R Maher | February 3, 2015

Estimated reading time 16 minutes, 37 seconds.

Have you heard that 50 is the new 40? Well, that’s what I’ve been told. I’m hoping this also means 62 is the new 52, but the problem is, I can’t seem to remember back that far as to what that felt like!
But what I do remember are the 18 years I spent flying the line in the ever-young Bell 412. It’s sometimes hard to believe that this incredibly capable helicopter was spawned from a design dating back to the ‘50s in the form of the Bell UH-1.
What’s kept the airframe fresh over the years is a fairly regular evolution in its design. This has taken it from the UH-1N Twin Huey and its civilian 212 variant through to the 412 (four blades instead of two, offering improvements in speed, range and hover capability), 412SP (Special Performance — included a 50 percent increase in fuel capacity), 412HP (High Performance — with increased transmission capability and optimized engine performance), and the 412EP (Enhanced Performance — with upgraded electronics and raised one engine inoperative power ratings for improved Category A capability). Last summer, I had the opportunity to fly the latest variant of this storied aircraft, the 412EPI, at Bell Helicopter’s headquarters in Fort Worth, Texas.
The fundamental differences between the 412EPI and the 412EP are the engines (electronically controlled Pratt & Whitney Canada PT6T-9s replacing the PT6T-3Ds), the factory-installed BLR Aerospace FastFin System (previously available through a supplemental type certificate for the 412EP), and the inclusion of the Bell BasiX Pro fully integrated glass flight deck.
It’s sometimes hard to believe that this incredibly capable helicopter was spawned from a design dating back to the ‘50s in the form of the Bell UH-1.
Understanding Airflow
The 412EPI’s FastFin System performs two basic functions, with two distinct elements. In a conventional helicopter, such as the Bell 412, the main rotor airflow during a hover comes down vertically over the tail boom from right to left (from the perspective of looking forward from the tail boom). Accordingly, the tail boom actually acts like a wing, producing “lift” in the same — and unwanted — direction as the main rotor torque. The FastFin’s two strakes, installed along the left side of the tail boom, break up and then organize the airflow on the low pressure side of the tail boom. This combination of first breaking up the flow with the top strake, then organizing the residual flow with the bottom strake, reduces the demand for left anti-torque pedal.
The second element of the FastFin is a modified vertical fin. The surface area of the aft vertical fin is relocated lower and further aft of the conventional tail boom, allowing a notch to be cut out of the aft area of the vertical fin — an area that previously blocked a good portion of the major thrust generated by the tail rotor. Tail rotor authority is not only increased, but also by maintaining the same — but relocated — tail fin surface area, the helicopter keeps its original handling qualities for maneuvers such as run-on landings.
In spite of its 11,900- pound gross weight, the Bell 412EPI is still highly maneuverable and fun to fly. Its BLR FastFin system also allows for considerably more load to be carried in hot and high conditions.
The combined effect of the two elements of the FastFin System is a significant improvement in hot and high hover in ground effect performance — by as much
as 1,250 pounds (a 91 percent increase) according to BLR — even though the max gross weight remains the same. The positive change to the weight/altitude/temperature (WAT) chart, combined with increased wind azimuth tolerance, means that even though the altitude and/or temperature may rise, the lower power demand from the tail rotor combined with higher wind limits allows more weight to be carried at those higher altitudes.
But, while the performance gains of the FastFin System are impressive, it’s when you climb into the cockpit that you see just how new an animal the 412EPI really is.
You are greeted by the integrated avionics system centered on two sets of identical Rogerson Kratos high resolution display units — à la the Bell 429. The primary flight displays (PFDs) are mounted directly in front of the pilots, with the pilot and co-pilot multi-function displays (MFDs) mounted to the left and right, respectively, of the PFDs.
Improved tail rotor authority is one trait of the 412EPI, thanks to the FastFin system, which is installed as standard.
In the center of the instrument panel sits the new generation Garmin GTN 750 — combining functions such as navigation, communication, and a wide area augmentation system (WAAS) GPS with a large high resolution moving map. The 412EPI is single-pilot instrument flight rules (IFR) approved with the standard three-axis, or optional four-axis, automatic flight control system (AFCS). The remaining King Gold Crown avionics are mounted on the updated lower center pedestal.
In the 412EPI, the inverters only power the AFCS. And, with such a modernized panel packed with expensive avionics, I had hoped to find an avionics power switch; alas, none was to be found. Fire suppression no longer requires those big T-handles. Now you just push a button to engage the system and then select to fire the main and/or reserve fire bottles.
In spite of all the modernization, my hands still instinctively fell to the proper places to operate the various systems switches and controls. 412EPI transition will be a breeze for 412 pilots, and especially so for 412EP pilots.
The new glass panel displays the customary flight and navigation information, as well as engine and rotor drive system indications. Other offerings include electrical, hydraulic, and fuel system graphic display and monitoring; all crew alerting systems; a full-blown and easy-to-use weight and balance system; automated power assurance, Category A performance, and hover performance calculations; health and usage monitor- ing system (HUMS), maintenance, and diagnostics data; and display of WX Radar, forward looking infrared, traffic collision avoidance system (TCAS), terrain awareness and warning system, and video inputs. It also incorporates an outstanding training mode. Suffice it to say, the steam gauges are gone!
The 412EPI retains the near- bulletproof soft-in-plane main rotor system of all generation 412s.
System Checks
My guide and safety net for my evaluation flight was Bell pilot Dave Salem. Firing up and getting the 412EPI ready to fly was straightforward. In terms of time to get airborne, the integrated avionics system seemed to be on par with the traditional steam gauge panel. Some of the basic systems checks are consider- ably shorter, but there is the needed time for self-tests that the new electronic system must complete. However, what was clear to me was that the required checks and preparation for flight seemed much simpler.
Starting the 412EPI’s PT6T-9 Twin-Pac engines was typical PT-6, except for one bonus: with the electronic engine controls, you now have automatic start with hot start protection. Push the starter and watch. The upgraded powerplants can deliver 1,825 shaft horsepower (s.h.p.) to the transmission at a maxi- mum continuous mast torque of 81 percent, and 1,928 s.h.p. for the five-minute takeoff mast torque of 100 percent. The maxi- mum available 30-second one engine inoperative (OEI) shaft horsepower is 1,269 at 81 percent torque.
Hydraulic checks? Watch the system on the MFD, then pull up the fuel schematic for the fuel system check. Salem turned off boost pump number 1 and I watched on the screen as the schematic showed the pump inoperative and the cross feed valve opening with a corresponding message. The extended “fuel dance” one has to do on the basic 412s is now pretty much eliminated. Other pre-takeoff functions follow suit.
With takeoff checks complete, the rotor was brought to 100 percent, and we turned on radar and TCAS on the MFD. Those functions took the top half of the screen, and the engine management and torque occupied the screen’s bottom half.
Running on the ground just before takeoff, the MFD was showing measured gas temperature (MGT) as “boxed in” which indicates that MGT is the first limit. However, depending on specific conditions, that can change as soon as you start pulling pitch. But with the power situation indicator (PSI), which displays the critical limiting parameter, as long as you keep it within the proper range for the specific operation, you’re fine.
Salem and I set barometric pressures on our respective PFDs and I disarmed the force trim. I, along with many 412 pilots, prefer this when I’m going to be hand- flying — it means I don’t have to continuously depress the force trim switch every time I want to move the cyclic.
The 412EPI all-glass panel is anchored by two sets of Rogerson Kratos high resolution display units, separated by a Garmin GTN 750 in the center.
Taking to the Air
It was a typical hot and humid afternoon in the Dallas, Texas, area for my flight. Loaded to within eight percent of the 412’s 11,900-pound maximum gross weight, the pick-up to a hover — and brief maneuvering for a few photos from Vertical publisher Mike Reyno — quickly made me feel right at home.
Following a normal takeoff, we headed out to the practice area. As soon as we passed through 70 knots, the rotor RPM automatically reduced to 97 percent — an action that was previously required by the pilot through a beep switch on the collective. Now there is a collective-mounted RPM switch that can be placed in “Auto,” “100 percent,” or the “103 percent” position (used for Category A procedures). Of course, 97 percent is preferred for normal operations because it’s more efficient, smoother, and quieter.
I did a quick cruise check at 2,000 feet, 100 percent rotor RPM, and 75 percent torque; our true airspeed (TAS) was 127 knots. Dropping the RPM back to 97 percent knocked off a couple of knots, but the ride sure was nicer. The MFD does display TAS, but I also crunched the numbers later just to be sure.
The author experienced rock solid tail rotor control even at a sideways flying speed of 45 knots.
My next test was hovering out of ground effect (HOGE). I positioned into the wind, which was 14 knots at altitude (as displayed on the wind vector on the MFD), and confirmed being stationary over a landmark. Left pedal displacement was definitely less than I was used to in my 412 flying. Then I began a left pedal turn, and found I was expending less pedal displacement during the turn than in the standard 412. As I passed into the downwind condition then continued on, the turn remained very stable and smooth; there was no tendency for the tail to want to whip or buck with pedal reversals. The turn was rock solid.
The critical wind azimuth for the 412EPI gained a full 10 knots at sea level over the non-FastFin equipped 412s — from 35 to 45 knots. This delta remains roughly the same until about 7,500 feet, where the FastFin limit stops at 35 knots; the stock 412 limit continues to drop down to 20 knots.
The one exception is that for the 412EPI the wind limit is down to 30 knots when it’s a tailwind from 30 degrees left to 30 degrees right of the tail. However, this is not a controllability issue. Rather, it’s due to an exhaust gas circulation issue and its effect on engine cooling.
The 412EPI is powered by the digitally-controlled Pratt & Whitney Canada PT6T-9 Twin-Pac.
Training Time
It was now time to sample the OEI training mode. Placing the “OEI TRNG” switch to either the 1 or 2 position selects the engine to be “failed.” The engine control units will manage the power output of both engines to behave as if the power were coming only from the “good” engine.
Salem set up our displays so that his MFD showed what the engines were really doing, while mine displayed the simulated OEI situation. Remarkably, when Salem hit the switch, the engines actually had that “spool down” noise signature that sounded like an engine had truly failed.
I pulled collective to 105 percent and entered the two-minute range. The PSI needle went into yellow and I heard a gong. If I had hit the blue ball marker, indicating I was at my 30-second limit, it would not let me exceed that limit. Rather, it would begin dropping the rotor RPM. However, there is a switch on the collective that allows the pilot to select the two-minute limit range to prevent going onto the 30-second range.
If we had pulled the rotor down too far with too much power, or if we had a real engine failure during the process — or if we had an electronic engine controller failure — the system would come out of OEI training mode.
Out of curiosity, I tried a HOGE to see how the aircraft would do. Its OEI performance was really good. We never left the low end of the two-minute limit range. We were hovering at 73 percent, with a maximum available torque of 81 percent for 30 seconds.
For training purposes, this is excellent. Not only does this safely allow for effective in-aircraft emergency training, but it’s especially beneficial for guys doing hoist operations; they can go into a HOGE at their typical weight and conditions, and see if they can sit there and bring that guy back up on a cable if the engine quits.
With that done, it was time to head back to the airport. While doing so, we received a traffic alert on both the 750 and MFD displays. Salem and I looked around and quickly found the threat. Nice.
We then brought the AFCS on line to play with. Altitude
was captured, NAV was engaged, and selecting “FMS” on
the PFD immediately caused the start of a turn for the airport. Operation of the system was pretty intuitive, with multiple ways to set the aircraft up for various approaches, including coupled LNAV/VNAV.
The 412EPI turned in cruise speeds of 125 to 127 knots during the author’s flight test.
Playing a little more with the MFD, we addressed having an electrical issue, such as a generator failure. With the systems display, you can see the essential, non-essential, and emergency busses and immediately tell what’s going on. It’s the same for fuel system issues — like losing a boost pump.
You clearly see what’s happening, and life is made so
much simpler. There is a lot to learn to get the most out of
the modern glass system, but just playing with it during my flight revealed that basic day-to-day system and NAV functions were quite intuitive in operation.
Back at the airport, I wanted to try some sideways flying. I first went sideways into an eight knot wind directly from my right. With a GPS groundspeed of 37, I was, in essence, flying sideways at 45 knots. Trying it to the left, this time into a 12 knot wind, the GPS showed 32 knots over the ground for a 44-knot total. And the ride and handling couldn’t have been more solid.
Three hundred and sixty degree pedal turns in the 12 knot wind were smooth and consistent, with not even a hint of the tail wanting to get loose — or “weather-cocking” — when turning into the tail wind.
Next, I performed a vertical takeoff, pulling 97 percent torque to generate a rate of climb of 1,500 feet per minute. Left pedal pressure was clearly not as much as I have experienced doing the same maneuver in a non-FastFin equipped 412.
Following that takeoff, we entered the downwind leg and engaged the RADALT hold function on the AFCS at 820 feet above ground level (AGL). Next, heading hold was engaged to direct our course on downwind with the heading bug. Selecting IAS (indicated airspeed) and beeping back the trim switch on the cyclic, the speed began to decline.
Once the speed fell below 60 knots, we engaged the vertical hold function. Salem also told me to take my feet off the pedals. Using nothing but collective and cyclic trim switches to control all axes of flight,
 I beeped the speed down into a stationary position while lowering to our desired 500 feet AGL.
The AFCS controlled power as necessary to hold our exact altitude. Point in space positioning was GPS- based, rather than Doppler, but it was spot on. Two little buttons were all I needed to maneuver the 412.
With the evaluation completed, all I was left with was a final steep 270-degree turn to position correctly for the approach to the parking pad — a last quick blast of fun before the party was over.
In my opinion, there is not a medium twin-engine helicopter that represents faithful “start, run, do the work, get me home” service better than the 412. With the 412EPI, Bell has taken a good aircraft and, with state- of-the art electronics, brought it into the 21st century. Accordingly, they have made it a better, more capable performer — and yet simpler to fly.
Once seriously rumored to be on the production chopping block about 10 years ago, the Bell 412EP has beasted through those troubled times to re-emerge,
in the form of the Bell 412EPI, as one of Bell’s major power players on the order books and bottom line. That’s an accomplishment that is sure to make its baby brother, the 429, very proud.

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