According to the contract between IFC and Cubana de Aviacion, deliverable examples of the An-158 going to the Island of Freedom, must be able to operate from airports with elevation above the mean sea level of no less than 3,000 meters. In order to confirm the airplane’s compliance with this customer requirement, the sides agreed to carry out proof testing on the third deliverable example of the An-158. This airplane was handed over to the airline at MAKS’2013 airshow, held August 27 – September 1, 2013. For the duration of flight tests, this airframe was outfitted with special test equipment for accurate measurements and data recording.

During preparation phase, IFC, Antonov, engine developer Ivchenko Progress and engine manufacturer Motor-Sich (the latter two leading the project of the D-436 motors powering the An-148/158 aircraft family) conducted a joint study into hot-and-high capabilities of the airplane. Jointly they come up with a suggestion to break the flight test campaign into two phases. First is to conduct ground runs at an airport with the elevation of 3,000 meters, and – should those come to expectations – to proceed with tests at another airport, with elevation of 4,000 meters. The Cuban side accepted the plan.

An international team saw to the trials. Tests themselves were carried out by Antonov specialists. Senior flight test pilot Sergei Troshin and test pilot Andrei Gorin were the main characters on the stage. Besides, there was another highly experienced test pilot onboard: Igor Chernov from the State Scientific-Research Institute of Civil Aviation (GosNII GA). Watching the trials were a number of flight safety inspectors from Russia, Ukraine and Cuba. Under a prior agreement with the Cuban side, assistance was provided by airport administration, air traffic control and aircraft handling agents in Ecuador and Bolivia (services, slots, fuelling, parking etc.).

The first phase of trials took place in Ecuador in the period of November 8-14, 2013. A number of tests were done at the airport of Latacunga. This place had been previously used to conduct similar testing on the Ilyushin-96 and Tupolev-204 jetliners. The airport of Latacunga has elevation over the sea level of 2,806 meters. During testing ambient air temperatures fluctuated between +11 and +21 degree Celsius. Deviation from the International Standard Atmosphere (ISA) varied between +8 and +18 degrees.

Yuri Ostrovski recalls that the main work at Latacunga was to get the engines and auxiliary power units (APU) starting, and doing so with a large variety of settings and adjustments. Various models of aerodrome power units were tried to get the engine starting. A total of 28 successful engine starts were achieved. In the process, a thorough assessment was done on all aircraft systems.

During testing, the industry team and the inspectors watched closely parameters of the engines running at normal modes and going through interim regimes, as well as parameters of the lubrication and other onboard systems. Ostrovsky claims that the D-436 engines and AI-450 APU worked as per description in the Aircraft Manual and other guiding documents available for the airplane. At this stage of trials, no deviation from normal functioning was registered, as far as avionics, air conditioning and other onboard systems are concerned. The inspectors present at Latacunga were able to make sure that all onboard systems of the airplane functioned as per description in the manufacturer’s manuals.

According to Ostrovsky, all ground tests in Latacunga were done completely in accordance with the original schedule approved by the Cuban side. “The airplane showed itself very well, for it operated in strict compliance to the manuals”, he stated. This fact allowed the international team to proceed to the second phase of trials. Ostrovsky comments: “At this point we decided not to go with our trials at Latacunga further than ground tests. Instead, we would rather go to La Paz. This way of conducting trials had been prior agreed with the Cubans: our original agreement had been that if everything goes right at Latacunga, we would rather proceed in another airport and in more demanding environments”.

In the period of November 15 -22, the international airport of La Paz, serving the capital city of Bolivian Republic, provided testing grounds for the An-158. Its proper name is El Alto International Airport (Spanish: Aeropuerto Internacional El Alto) (IATA: LPB, ICAO: SLLP). This airport has elevation above the mean sea level of 4,058 meters.

In addition to the higher elevation, the move to Bolivia brought about an increase in the ambient air temperature. The actual readings there varied between +10 and +18 degree Celsius, but after being adjusted to the International standard atmosphere (ISA), the temperature rose by +21… +29 degree Celsius and almost to the maximum advertized temperatures in the aircraft guiding documents (ISA+30). All this created a much more demanding environment as compared to that in Latacunga. It is well known that the thrust of dual-flow turbofans with high-bypass ratio – and the D-436 is one of those – depends on altitude and ambient temperature, with its factual readings going down as the former and latter grow.

Again, the work on the airplane commenced with some ground testing. The engines proved their merit by switching on and off smoothly in all cases, for a total of 52 starts done at La Paz. Together with those done at Latacunga, the grand total comes to 80. Hot and cold engines were started, with poor and rich settings of the fuel mixture. Ostrovsky claims that in all cases the actual readings of gas temperature peaks and time period [to start the engine] appeared a bit below the respective “red line” figures in the Aircraft Flight Manual.

Ostrovsky points out that an issue arose with starting hot engines. When the temperature of hot gases inside the motor was in the region of 150 degree Celsius (a practice equivalent to “starting a hot engine”), the power plant sometimes failed to start. This made Antonov, Ivchenko Progress and Motor-Sich to issue a note for the airlines operating the type. The doc notifies them that in the conditions similar to those observed at La Paz, the D-436 engines, after being switched off, need to cool down to 110-120 degrees Celsius in order to get sufficiently cool for a reliable starting.

Having completed the ground runs, the team proceeded to flight trials. In accordance with the original schedule, a total of five test sorties were made. The test pilots performed several passes over the runway during each flight, in order to attest aircraft performance in various flight configurations (clean, flaps down, flaps fully down) and conduct checks for proper functioning of onboard systems. Real-life assessment was given to various possible cases, including partial loss of thrust in a simulated engine failure. Takeoff performance of the aircraft was thoroughly accessed, including rejected (aborted) and continued takeoffs after a simulated failure of the critical engine. In other words, the test pilots evaluated behavior of the aircraft in a number of situations that might be observed in everyday airline practice.

“We have tried a number of probable scenarios, both normal operations and failures. The inspectors were able to make sure that the airplane’s behavior is fairly close to the predicted one as foretold with help of some calculations done before the flights”, Ostrovsky says.

The results of the tests together with some important readings of major parameters were made into a protocol signed by the industry and the inspectors. This document comes with a preliminary conclusion which states that all tests originally agreed by the provider of the aircraft, the aviation authorities and the customer have been completed.
 

The data gathered during the test campaign provides sufficient ground to assert that the real [factual] field performance of the An-148/158 family aircraft comes fairly close to the figures given in the airplane’s Flight Manual. In particular, the data collected provides proof to the manufacturer’s early promise to the customer that the An-158 can safely operate out of the airport with elevation of 4,000 meters above sea level with the manufacturer-specified gross weight for the given atmospheric conditions. The flight-testing done was to make sure that in such circumstances the An-158 possesses enough thrust to stay in climb with the prescribed gradient after experiencing an engine failure at takeoff.

Ostrovsky makes a point that the testing done at Latacunga and La Paz took relatively short time, proceeded without failures and drew to a close with some positive results. The data collected is also applicable to the An-148-100, being the baseline model of the plane that won the type certificate of ARMAK (the civil aviation authority of Russia and other countries that are members in the Commonwealth of Independent States). The An-158 is a derivative of this baseline model, and the holder of a complimentary type certificate.

In practice, the flight-proven capability of the An-158 allows airlines operate the type out of hot-and-high airports on revenue services. Should a need arise, the airplane can operate, say, out of La Paz on services to all major airports in Bolivia (Santa-Cruz-de-la-Sierra, for example) with some fifty passengers on board. Degradation of An-158 payload-range performance to higher runway elevation goes on with the rates similar to those observed on Boeing and Airbus jetliners.

Upon completion of the flight test campaign in Ecuador and Bolivia, the third deliverable An-158 flew back to Cuba and resumed revenue flights. The national carrier, in cooperation with the aircraft manufacturer and the leasing company, has formed a capable technical team in Habana’s Jose Marti Airport able to provide trouble-free operations of the newly acquired Antonov jetliners on charter and scheduled passenger services. In November 2013, the type’s monthly utilization rose to 170 hours per airframe. The airline and the lessor are all set to increase the utilization further, building on the successful experience amassed by Rossiya and other early An-148 operators in Russia and Ukraine.

“From interactions with the airline personnel, I learn that the Cubans are very happy about their new airplanes”, Ostrovsky asserts. In addition to domestic services, the An-158 has recently commenced flights to the Bahama Islands and Dominican Republic. With the fleet now comprising three aircraft, the Cuban aviators can further expand their network of air routes. They consider services to Venezuela, Costa-Rica and Mexico. So, the An-158 is ready to bring a new dimension to the air travel in the Latin America and the Caribbean.

The flight test campaign in Ecuador and Bolivia helped the joint team of Russian and Ukrainian companies behind the An-148/158 project promote their product in the region. During the trials a number of local airlines approached IFC and Antonov to express an interest in the aircraft. Representatives of some local airlines watched the Cuban An-158 closely as the aircraft was going through its paces during the flight test campaign. Their interest can be partially explained by the fact that the An-158 is, in fact, the first passenger plane from Russia/Ukraine with the advertised ability to operate from airports with elevation of 4,000 meters. Operating out of such “problematic” airports, the An-148/158 can provide some competition to the airplanes made in the USA and EU flying in the region today.

The success that the lessor has so far had in the region is limited to the sale of six An-158s to Cuba. Today, three such aircraft are in the inventory of Cubana de Aviacion. They feature a single-class cabin layout with 97 seats at 32 inches pitch. Following acceptance of the third deliverable An-158 at MAKS’2013, Cubana de Aviacion placed follow-on order for three more aircraft. These will be provided via IFC on financial lease terms. Airframes of these three additional An-158s have already been assembled at the aviation plant in the Ukrainian capital city of Kiev. They are being outfitted with vendor items. With the An-158 fleet growing to six aircraft, Cubana de Aviacion is able to further expand revenue operations on the type. In addition to the already mentioned services to Mexico, Ecuador and Costa-Rica, the airline has plans to open flights to Honduras, Nicaragua, Trinidad and Tobago, and, in 2015, to Panama.

The flight tests done in November provide ample factual data that shall be used in the process of issuing a complimentary certificate to the An-148/158 type certificate so as to enable revenue operations of these jets in the attested conditions.