Near the end of the official three (3) day State Visit of President Rodrigo Duterte to South Korea in June 2018, he visited the aircraft manufacturer Korea Aerospace Industries (KAI) where he was shown the KUH-1 Surion Helicopter. Duterte also got to ride the aircraft for around five minutes and was reportedly impressed by it, but left it to the Technical Working Group (TWG) of the Philippine Air Force to review the proposed acquisition of the aircraft.1 2
Other government officials later added more details about the possible acquisition, with Department of National Defense (DND) Secretary Delfin Lorenzana putting the number to be purchased to be as low as eight (8) while National Security Adviser (NSA) Hermogenes Esperon Jr. putting it to be as high as twelve (12).3 With this, let us take a closer look at the Surion.
The Surion is a twin-engine Transport Utility helicopter and is the first home-made helicopter by South Korea. It was developed and built by KAI with technical assistance from the European company Airbus (previously known as Eurocopter). It is a very new aircraft, it first flew only in 2010, and entered service with the South Korean armed forces in 2013.4
The Surion is reportedly based on the EC155 (now known as the H155) and Puma family helicopters made by Airbus,5 although externally it looks more like the latter. As of now only South Korea is operating the aircraft, with 65 units already delivered and 220 more ordered by their Army and Marines.6
PILOTS AND PASSENGERS: Assuming with two Pilots and the rest being Passengers, the Surion can be configured to carry a maximum of seven (7) more passengers than the Huey and five (5) more than the Bell 412.
PILOTS AND TROOPS: Troops with their equipment are heavier and occupy more space, hence compared to ordinary passengers, helicopters will be able to carry less. Assuming with two (2) Pilots and two (2) Machine Gunners, the Surion can carry four (4) more troops than the Bell 412 and up to six (6) more than the Huey.
CRUISING SPEED: The Surion is 36 kph or 15% faster than the Huey and 14 kph or 6% faster than the 412EP in terms of Cruising Speed which is a significant advantage over the Huey and the 412EP.
EMPTY WEIGHT (EW): Here we can see that the Surion is a much bigger aircraft, being more than twice as heavy in term of EW as the Huey and around 38% heavier than the Bell 412.
DISC LOADING:11 Being the heaviest aircraft between the three, the Surion also has the highest disc loading which is 42% more than the Huey and 21% more than the Bell 412, indicating less maneuverability than either aircraft.
Being a much bigger aircraft, I expected the Surion to have better range than the Huey or the 412EP, but surprisingly, the opposite is true as it has a much lower Internal Fuel Factor (IntFF)12 and therefore potentially 28% less range than the Huey and 42% less than the Bell 412.
The reason for this is that while the Surion is a much heavier aircraft, it doesn’t carry as much fuel as it should compared to its Maximum Take Off Weight (MTOW). For example, it only carries 297 kg more fuel than the Huey, and in the case of the Bell 412 it even carries 69 kg less fuel.
The T-700 engines of the Surion though does have a lower Specific Fuel Consumption (SFC) than the T-53 engine of the Huey (13% lower) or the PT-6T engines of the 412EP13 (23% lower), but the differences aren’t higher than the difference in IntFF. So even if those are factored in, I think the Surion will still have around 15% less range than the Huey and 20% less than the 412EP.
However, we have been using the Huey for decades now, and it has done well, its range doesn’t seem to have been an issue with the Air Force and the Surion seems to only have marginally less range than it, so this might not necessarily be a deal breaker for the aircraft.
The Surion has twin engines, the same as the 412EP. In theory this gives both aircraft a better margin of safety than the single engine of the Huey. The Surion’s engines though are around twice as powerful as that of the Huey or the 412EP, and they also have Full Authority Digital Engine Control (FADEC) as opposed to the mechanical controls of the Huey or the 412EP’s engines.
In theory this allows the Surion’s engines to operate at maximum efficiency and safety at all times since a set of computers are always monitoring and optimizing their performance. It also allows easier checking and diagnosis since the engines’ performance history is logged and tests can automatically be made if needed. On the downside though, FADEC also means a more complex system to maintain.
’Built In Features’
One thing I noticed about the Surion is that it has a lot of built in survivability and night capability features in place, and these include the following:14
– The Cockpit and Frame are armored to resist hits by up to 7.62 mm caliber ammunition
– The Fuel Tank is Self-Sealing and armored to resist up to 14.5 mm caliber ammunition
– Redundant Rotor Control System
– Laser, Radar and Missile Warning Receivers or Systems
– Countermeasure Dispensing System (CMDS, for Chaff and Flare)
– Helmet Mounted Display (HMD)
– Forward Looking Infra-Red (FLIR)
– Infra-Red (IR) Suppressor Exhausts adapted from the H225M15
On the other hand, the only survivability feature I know of on the Huey are its bullet resistant seats and self-sealing fuel tanks.16 The 412EP seems to have even less features, but of course most if not all of the above features could also be incorporated into the Huey and 412EP if needed, but at added costs and weight penalty to the aircraft.
All these systems on the Surion are nice to have, especially if you are fighting against a strong enemy, like an army of another country, for example. And South Korea has long been in a state of war with North Korea, so this is the reason why the Surion was designed this way with a lot of features.
’Full Night Capability’
The HMD and FLIR allow much easier and safer night time operations and gives it full night time capability. As of now only the AW109 helicopters have this capability among the helicopters of our armed forces, and they don’t have HMDs, so the Surion has one up over them.
The HMD used by the Surion is the ANVIS/HUD-24T made by the Israeli company Elbit Systems.17 Below is a video of how it works with the FLIR to provide the Pilot with excellent night vision:
I’m not sure though if all these survivability and night capability features are required by our Air Force for their Transport Utility helicopters because when we bought the 412EP back in 2014, these doesn’t seem to have been included. All these equipment also add more weight, complexity and cost to the aircraft. But should the Air Force require them, then the options are there already.
Being a much heavier aircraft and with more powerful engines, I expect the Operating Costs or Cost per Flight Hour (CPFH) of the KUH-1 to be much higher than any of the helicopters we are operating now.
Unfortunately, I wasn’t able to find any CPFH figures specifically for the Surion, but we may be able to get a rough estimate of its CPFH by looking at similar figures from the Puma family of helicopters which the Surion was based on.
In terms of Empty Weight and Engine Power, the Surion is closest to the AS332, and the available CPFH data is for it is its AS332L1 stretched civilian version which is USD 2,700.18 This is almost twice higher than the USD 1,405 CPFH of the Huey19 and the USD 1,586 CPFH of the 412EP.20
’Wheels and Soft Ground Performance’
Unlike the Huey or the 412EP, the Surion uses wheels instead of skids for its landing gear. The reason for this is because beyond a particular weight (approximately placed at 3,600 kg Empty Weight or EW by one source), a helicopter would be too heavy already to move around on the ground if it only has skids, hence the need to start using wheels.21
The Surion has an EW of 4,975 kg, way above the 3,600 kg limit mentioned above while the 412EP has an EW of only 3,084 kg. Even Bell Helicopter, the maker of the 412EP, uses wheels for its helicopters that are heavier than the 412EP like the Bell 525.22
There are advantages and disadvantages between skids and wheels which I covered in my blog about the H145 helicopter,23 but to add to that would be the issue of performance over soft ground.
Skids have a larger Surface Area to distribute the weight of the helicopter compared to wheels, hence the weight per square area (or the Ground Pressure) of skids will be lower than with wheels. This enables skids to be able to stay on top of softer ground and not sink compared to wheels for the same weight.24
In the case of the Surion, not only does it use wheels, it also is 38% or 3,305 kg heavier than the 412EP in terms of MTOW, giving it a much higher Ground Pressure thus making it more likely to sink on soft ground.
But this can be managed, I think our Air Force is already doing Soil Hardness Tests and mapping the areas where their helicopters can land in the areas of operation, thus they just need to factor in a heavier aircraft into their mapping.
’Cabin Door Size’
One issue I felt I needed to consider was the size of the doors of the Surion since the previous administration under President Benigno Aquino Jr. rejected the W-3 Sokol helicopters bought by the administration of Gloria Macapagal Arroyo for that issue.
They found that the door of the Sokols were too small to accommodate both the gunner and the embarking or disembarking troops at the same time, which is not the case for the Huey and the 412 since they have the widest doors for their weight class. This eventually led the Sokols being pulled out of combat duty and relegated to Search and Rescue operations.25
In the case of the Surion, I could not find any references in the internet for its exact door size, but from the pictures and videos, it seems that the doors are bigger than those on the Sokols. Also, the Surion have dedicated mounts and positions for the gunner right beside the doors, so they will not be competing for space with the entering or exiting troops.
So fortunately, the Sokol door issue will not be a problem with the Surion. Below is a nice walk around video of the Surion from Youtube showing its door openings and Machine Gun placements:
To summarize, in terms of good points, compared to existing Air Force helicopters, the Surion is faster, can carry more Troops, are better protected (Armor, Self-Sealing Fuel Tanks, IR Suppressed Exhausts), have good Warning (Laser, Radar and Missile Warning Systems) and Countermeasure (Chaff, Flare) systems, better Avionics (FADEC), full night capability (HMD, FLIR), have redundant controls, have wide doors and separate positions for the Machine Gunners.
On the downside, it has less maneuverability, expected lower range, higher Operating Cost, and less Soft Ground Performance than the Huey or the 412EP. In fairness, the Soft Ground issue is not limited only to the Surion, though, but to all helicopters heavier than the 412EP.
Personally, if all of the issues of the aircraft I wrote about in a previous blog26 have really been solved, then the Surion could still be a good helicopter for us. If we get them with all the features, then we will have a helicopter we can be confident with even against external armies, and a bigger transport helicopter that can operate fully even at night.
However, the crash of a variant of a Surion, an MUH-1 Marineon which killed five (5) people and injured one27 as I was finishing this blog could have a negative effect on the chances of the Surion being bought by us.
Still, I wish KAI and the Surion luck, I hope they are able to clean up and solve all of their problems soon.
Duterte Impressed with Korean-made Surion Helicopters,
‘Duterte is Looking into the Purchase of Military Equipment from S. Korea’ — Roque,
- Duterte Impressed with Korean … ↩
Army Deploys Surion Copters,
Surion: Eurocopter’s Korean KHP/KUH Helicopter Deal,
Flight International World Air Forces 2018,
Korea Aerospace Industries, Ltd – KUH-SURION,
Helicopter KAI KUH-1 Surion Republic of Korea Army,
- Disc Loading here is computed by dividing the Maximum Take Off Weight (MTOW) of the helicopter with the Area of its Rotor. ↩
- Internal Fuel Fraction is computed by dividing the Total Weight of the Internal Fuel of the aircraft by its MTOW. ↩
Flight International 8-14 June, 1994 – Turbine Directory,
- Korea Aerospace Industries, Ltd – … ↩
Asian Military Review – July/August 2016 – p. 33,
Yanks – Bell UH-1H Huey,
- Surion: Eurocopter’s Korean KHP/KUH … ↩
Conklin and de Decker AS332L1 CPFH,
Conklin and de Decker UH-1H Huey CPFH,
Conklin and de Decker Bell 412EP CPFH,
Skids or Wheels?
Bell 525 Relentless,
The H145 for the Philippine Armed Forces?,
Wheel versus Skids – Who Wins?
Defense Chief says Purchase of 8 Sokol Choppers from Poland is Last,
Surion Helicopter Problems up to July 2018,
Five Killed in South Korea Military Helicopter Crash,