As an operator of both aircraft, I am frequently asked what the difference is between the A109E Power and the A109SP Grand New.
Minor differences worth a quick mention: The newer A109SP has a few structural differences such as a composite fuselage and a slightly longer cabin. The A109SP has 2 of the newer Pratt and Whitney 207C engines rated 735 shp at takeoff power vs the older 206C models only rated 640shp at takeoff power. The 109SP allows for up to 107% Torque on take off for 5 minutes vs the 100% that the 109E permits. If you were allowed to use 107% in the older helicopter that would give you 685 shp per engine so the actual difference between the two aircraft is only around 50 shp per engine. Single engine power allowances go up slightly in the A109SP; 9% more for maximum continuous OEI torque, and 20% more for the 2.5 minute power range.
The gross weight in the SP has increased from 3,000 kg to 3175 kg, however; the vast majority, if not all of the extra payload is taken up with the weight of the new avionics. The FADEC and engine airframe indications are essentially the same. To a 109E pilot initially utilizing the EDUs (electronic display units) on the new helicopter, there are no immediately apparent functional differences. As one would expect there are some minor software upgrades such as the ability to record aircraft exceedances and data recording when performing power assurance checks.
The major differences come into play when discussing the flight instruments, automatic flight control system, and navigation system. It is in this area that a seasoned A109E pilot will do a serious double take when hopping into the cockpit of an A109SP. These items are not simply upgraded, but entirely new systems, GrandNew systems...
Agusta retained the skeletal system of the flight controls but completely replaced the brains of the system, trading out antiquated Vertical Gyros for two AHRS units, and the ancient 3 axis Sperry HELCIS II Flight Director with a brand new proprietary 4 axis dual autopilots.
Why 4 axis autopilots will always be better than 3: To fly single pilot IFR under FAR Part 135, we are required to have an autopilot as a second in command. The A109E model's autopilot is akin to having a 5 year old child sitting next to you who can perform all but the most basic tasks you ask of them. The A109SP's autopilot is comparable to having Yuri Gagarin sitting next to you, he's a freaking Astronaut, but he doesn't speak your language. (yeah I know he actually did, not the point!) No matter which type of system a pilot operates, the important thing about an autopilot is that it is in lieu of an SIC, one should never, ever give up their PIC authority to the machine.
The reason why I believe that a 4 axis autopilot is a giant leap forward in safety, is due to the amount of pilots I've seen forget to bring in power when it is time to level off in a descent or initiate a missed approach. I am not an accident investigator, but if you read the preliminary report on the accident in MN this past year, it's possible to speculate that the proper amount of power may not have been applied in the missed approach. CEN16FA372.
Of course this does not mean that the A109SP's AFCS will prevent accidents as seen by the fatal CFIT accident near Mexico City in July 2012.
An oldie but a goodie: For a pilot who is current and proficient at flying by hand in the clouds and only relies on the autopilot as a tool for stability and accuracy, the E model is sufficient and reliable for most tasks. As long as the pilot keeps a very close eye and their hands near by the controls the E model will hold either an altitude or an airspeed, and heading or navigation within ATP standards if there is no turbulence. It can also reliably and safely couple to basic ILS approaches. When it comes to Point in Space copter approaches with steep descents and mandatory airspeeds, and LPV approaches, the E model ranges from barely satisfactory to incapable.
Wiz Bang! For a pilot who is a expert systems manager and desires the advanced capabilities of the latest instrument flying technology the A109SP's autopilot really shines. The autopilot in the SP will couple flawlessly to airspeed, altitude, and lateral navigation simultaneously, while also displaying this information to the pilot. I have seen the E model struggle to hold + or - 10kts of airspeed while it leaves the pilot questioning what airspeed they initially asked it to maintain. The SP will hold the airspeed with in 2 to 3 knots only allowing slight excursions for comfort of ride. The SP's autopilot will couple to an LPV approach, fly past minimums to 75ft above the runway and level off, at which time the pilot can engage hover mode, slowing and descending to a level, stationary hover.
Aside from the steep learning curve presented by the new autopilot, the disadvantage of going digital is the number of faults that leave the autopilot incapacitated. For aeromedical operators this raises concerns as hospital helipads often have MRI machines that present an extreme EMI interference on the AHRS. When the flight control computer reaches its tolerance for heading discrepancies it will no longer couple to lateral navigation. In this case, among many others, there is no CAS message alerting the pilot to the issue, and the only solution to clearing the fault is to power down the entire avionics system and reboot. This leaves a pilot who may not be nearly as hands on proficient as his E-model counterpart, alone in the clouds.
Switching from A109E avionics to A109SP avionics not only requires a pilot willing to undergo extensive training and study, it also requires a maintenance staff who are willing to sharpen their avionics skills and keep in close touch with Agusta tech support on software updates and troubleshooting.
Overall, I prefer the newer autopilot system over the old 3 axis, both due to safety of having coordinated power inputs and to the enhanced capabilities of the newer system. With that said, I also appreciate the opportunity to fly the E model, get back to basics so to speak, and strengthen the foundation of my instrument flying skills. Either way the key to success in single pilot IFR is to study, practice, and know the limits of your proficiency and ability to always stay at least two steps ahead of the aircraft.
You can learn more about the Agusta 109 from their website.
Next time I will compare the Cobham/Genesys navigation system in the A109SP to the older Garmin systems found in most A109E models.