One year of Tiger flight tests

EIGHTEENTH EUROPEAN ROTORCRAFT FORUM

C-03

Paper No. 130

ONE YEAR OF TIGER FLIGHT TESTS

by

P.

ROUGIER.

EUROCOPTER FRANCE

A.

TELEKL EUROCOPTER DEUTSCHLAND

September 15-18, 1992

Avignon, FRANCE

INTRODUCTION

ONE YEAR OF TIGER FLIGHT TESTS

by

P. ROUGIER,

EUROCOPTER FRANCE

A

TELEKI,

EUROCOPTER DEUTSCHLAND

The TIGER flight test programme has been unclertaken according to the following general principles (see Ref. 1 ),

- 5 prototypes have been scheduled anc three of those (PTI. PT2 and PT3) help develop the basic helicopter I.e. the vehicle anc its avionics.

~ PT4 helps develop the VJeaponry on the HAP version I.e. the French Army's ground support and protection version.

~ PT5 helps develop the common franco-German ant\~tank version HAC/PAH2

- Futhermore. PT2 I~ to be retrofitted Into an HAP version anc PT3 Is to be retroflted Into anc HAC version once the basic helicopter's development has been completed with those prototypes.

- Two test sites have been selected; Eurocopter France's Marlgnane facility for basic flight tests anc the HAP version's development; Eurocopter Deutschland's ottobrunn facility for the HAC/PAH2 tests.

- The basic helicopter's flight development has been entrusted to an Integrated Eurocopter France;Eurocopter Deutschlanc team designated Flight Test Integrated Team (FIT).

This paper presents the results obtained wllh the first prototype (PT1) from the first flight on Aprll27. 1991 to mid July 1992.

2 PTI CONFIGURATION

PT1 has been designed anc manufactured to fly In HAC/PAH2 external configuration I.e. with mast mounted sight anc piloting vlslonlcs In the hellclopter's nose. as well as In HAP configuration I.e. with a 30 mm cannon In the helicopter's nose ancl roof mounted sight.

Furthermore, dummies \Were provided of TRIGAT and HOT ant!- tank missile pods as well as MISTRAL or STINGER air- to -air missile pods for In-flight carriage trials (see Fig. 1).

Rather than the production helicopter's basic avionics, PTI Is eculpped with conventional Instruments anc an adapted SA 332 system of electrical generation. Pl1"s test Installation Is bullt up around two computers ; the first. designated CATINA, acquires

BASIC

HELICOPTER---~

"DUMMIES"

HAC/PAH 2

~[§]~

C> i i ·1-;

.'i

₀

MMS

HOT

TRIG AT STINGER

HAP

RMS MISTRAL ROCKETS CANNON

FIGURE 1 , EXTERNAL CONFIGURATION

parameters varying slowly I.e. attitude, altitude, speed and engine parameters ; the second designated SOCRATE acquires parameters varying rapidly I.e. stresses and vibrations.

Overall, the test Installation allows the recording Of approximately 600 parameters on board the helicopter, Including 60 In totaling axis on the main rotor.

Digital messages are processed either in real time after transmission by telemetry, or off~ line by the Eurocopter France Flight Test Department's calculation centre In Marlgnane, Every Pfl test flight has up till now been monitored by telemetry both for safety and test productivity Improvement reasons.

3 FLIGHT HISTORY

PTI has completed 91 flights In 94 hours Including 54 hours In HAC/PAH2 configuration and l 0 hours In HAP configuration. The key dates are :

· First flight on April 27, 1991

- Presentation at the Paris Alt Shew on June 13-22, 1991

- First flight with mast mounted sight (HAC/PAH2 version) on October 9, 1991

-First evaluation by French and German Atmy pilot's (CEV and WTD61) on December 12, 1991 - First flight In HAP configuration on June II, 1992.

1 0% of the development hours were flown, In accordance with the contract. by mixed Official Services/Industry or Officials only crews.

4 MAIN RESULTS

4.1 Flight envelope

It can now be considered that the original flight envelope has been explored or, at least. that part of the flight envelope which could be explored In the 'NeOther conditions prevallng

at

Marlgnane.

Figure 2 presents, with pressure a~ltude/lndlcaled airspeed coordinates, the envelope opened In level flight and dives. Figure 3 presents the load factor envelope stabilized In level flight or descent as a function of Indicated airspeed. The points presented on Figure 3 are the load factors the main rotor servo~controls power allows on a single booster.

As regards low speeds. the manoeuvrability limits were explored In lateral flight up to 60 kt (Figure 4) and rear ward flight up to 50 kt.

A 6350 kg reduced mass was demons1Tated In hover OGE and numerous flights were performed at 5.7 Toil-up weight, which Is thought to cover today every mission configuration of the heaviest version, HAC/PAH2.

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FIGURE 2 ' FLIGHT EIWELOPE • ALTITUDE • INDICATED AIRSPEED FIGURE 3 , FUGHT EIWELOPE • LOAD FACTOR • TRUE AIRSPEED

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FIGURE 4 , SIDEWARD FLIGHT - PEDAL POSITION Vs LATERAL SPEED

4.2 Performance

It proved possible, after mounting of the mast mounted sight. to check that power required Is in accordance with, or lower than. predictions with the mission equipment drag configurations.

Figure 5 presents a comparison between flight test and aerodynamic predictions.

The correlation Is proved to be satisfactory. as a result of the extensive wind tunnel tests that were undertaken withal/8th scale model in Marlgnane In 1989 and 1990 (Figure 6).

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(Mistral and Trlgat Pods)

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FIGURE 5 , LEVEL FLIGHT PERFORMANCE PREDICTION/TEST COMPARISON

4.3 Handling qualities

FIGURE 6 , TIGER 1/Bfh SCALE MODEL

The longitudinal static stability was analyzed at several e.g. configurations, and was found to meet FAR 29 requirements. Furthermore. records were made of the dynamic helicopter behaviour with cyclic stick, collective and pedals fixed, which helped determine the time to double amplitude of the phugoid oscillations (See figure 7).

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FIGURE 7, PHUGOID

Longitudinal sialic and dynamic stability were. generally, considered solisfaclory from the beginning of the f!ight trials with the horizontal stabi!lzer in the initial (aft) or forward position and, as explained in this paragraph, different factors e.g. maintenance will be token into account upon the final selection of this stabilizer position.

Transverse handling qualities ...ere analyzed by studying the helicopter's behaviour at different stabilized sideslips (dlt"'edrol and weathercock effects), The contribution of the horizontal stabilizer's endplates hcls, In particular, been quantified during n~ .. m1erous flights without end plates. All flight tests to date have been flown without any form of automatic stabilisation. However. a SEXTANT analog AFCS. different from the production helicopter's digital AFCS. Is fitted and foreseen to study the helicopter's dynamic behaviour and should help check the volldlty of the gains predicted before the PT2 and PT3 flights.

The TIGER's NOE combat ability ~s contractually characterized by typical manoeuvres designated «agresslve manoeu\lfeS» or «mission task elements». Most of these are derived from Ref. 2 and are, for example.

M Acceleration time from 0 to 60 kt forward M Deceleration time from 0 to 60 kt fOIWard M Acceleration time from 0 to 30 kt sldeVIOys M Deceleration time from 30 to 0 kt sideways

other manoeu11res Involve flying a ~<dolphin» manoeuvre. switching from +2 to Og, and slaloming between Imaginary stakes over a 15 m wide side band (Figure 8).

1 D O L P H I N - - - ,

/

I 2 JINKING (SLALOM)

/

I stakes

/

- MAXIMUM CONTINUOUS POWER - PULL -UP TO ": 2g

- PUSH-OVER TO Og

- ±

10'

ROLL AND YAW

2g

- 80kl

- 40'

BANK - 25m ±5m HEIGHT -15m WIDE BAND

3 180'

T U R N - - - , - INITIAL SPEED ": 120kl -30m HEIGHT -TIME~ 20s - FINAL SPEED ": 120kl - 30m ±15m HEIGHT

FIGURE 8, AGRESSIVE MAMJEWRES (MISSION TASK ELEMENTS)

These manoeuvres were performed with PTl. and the ease with which they can be performed shall have to be assessed by operators on the Cooper- Harper scale.

4.4 Vibration level

The TIGER's main rotor Is of the hinge less type with a flapping hinge offset eculvolent to 10%. Because of the mission ecuipment reculrement for low vibration level. a filtering system designated SARIB Is fitted and Is extensively described and validated in (Ref. 3 and 4).

After some flapping weight adjustments. excellent results were obtained at 4 per rev and 8 per rev as a function of speed (Figure 9) and load factor (Figure 1 0) ; SARIB also proved fairly Insensitive to rotor speed. at least In the speed range authorized by the engine governor and the autorotatlon speed range. PT1 complies with the specifications throughout the operating envelope explored today. both In the HAC version with mast mounted sight and HAP version with a 30 mm cannon In the nose. In order that the mast mounted and roof mounted sight operate satisfactorily. the vibrations cannot be too severe. for both linear and angular accelerations.

Two types of mast mounted sight supports. differing mainly In their rigidity, were tested In 1992. with the Intention of validating the ground test results and to establish a data base necessary for the design of a support optimised to meet the environmental reculrements (See Figure 11 ).

4.5 Ground resonance

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FIGURE 10: COCKPIT VIBRATION (4/REV) Vs LOAD FACTOR

FIGURE 11 , MAST MOUNTED SIGHT SUPPORT

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3

5 PROBLEMS ENCOUNTERED AND Pll MODIFICATIONS

5.1 Horizontal stabilizer position

It had been decided. when the helicopter YJOS being designed, to position the horizontal stabilizer very far aft on the fuselage to meet the following two objectives :

- Very low ancl even zero negative lift In hovering flight. because the stabilizer Is not concerned by the main rotor Induced airflow

- High longitudinal stability efficiency with a lever arm set to the maximum (tail unit - rotor centre distance).

The drawbacks of this decision beccme apparent trom the first flights. When the helicopter moves from hover to forward flight, the airflow Induced by the main rotor Is Impinges on the tall unit and ccuses the fuselage to pitch nose up the pilot must then move the cyclic sticK forward to counter this pitch-up moment. Overall. a slgnlflccnt change Is noted, as shown on Figure 12. In the longitudinal altitude and moment at 1 per rev In rotating axis on the main rotor mast. It was thus decided to move the horizontal stabilizer forward (See Figure 13). Flight tests demonstrated that pitch-up Is ccncelled and the mast moments ore reduced with the stabilizer forward (See Figure 12). To date. the horizontal stabilizer's size and position optimization has not yet been completed, because the objective Is to define an optimum configuration both for the HAP and HACverslonwiththelr different armaments. 10 Tela (deg)

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FIGURE 12o, LONGITUDINAL ATTITUDE

• ORIGINAL STAiiUZER , _

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ADVANCED STABILIZER

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FIGURE 13 :STABILIZER LOCATION

5.2 Tall shake

This phenomenon, VJell known on every modern helicopter prototype,ls generated by the separate air flo\oVS running from the centre of the rotor or some parts of the fuselage that excite the tall of the helicopter. and on TIGER, more specifically, the vertical fin. This results In unsteady vibrations of relatively low (1 per rev approx.) frequency especially felt In descent. As far as TIGER Is

concerned. the airframe mainly responds to the 2nd lateral mode (2 modes mode) of the fuselage (See Figure 14) Where the helicopter's nose and the pilot are subjected to significant movements vkllle the gunner remains unaffected.

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lAS (kt) NODAL SHAPE

FIGURE 14 : TAILSHAKE VIBRATIONS (FREQUENCY 1/REV)

The solution to this problem was a systematic wind tunnel scan In total pressure aOO turbUlence intensity downstream of the rotor centre. 1hls helped locate the 1urbu\ent vortices and their Impact on the vertical fin. lhese tests -were confirmed wtth smoke dlsplays (oil Injection Into the exhaust pipes) In flight. The wind tunnel study wcs judged to be satisfactory,

n

became possible to optimize the MGB cowling with a mock· up until the size of the turbulent vortices VIOS reduced and moved away from the centre of the vertical fin (see Figure 15). Once PTl"s MGB cowling had been modified accordingly flight tests confirmed the Improvement recorded In the wind tunneL

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FIGURE 15' TAILSHAKE VIBRATIONS IN LEVEL FUGHT

6 CONClUSION

One year ofTIGER frlst prototype flight tests helped explore to a large extent the operating envelope. The versatility of this prototype as regards armament configurations helped progressively to define optimum solution fOl both the ground •upport and ptotectlon (HAP) and the anti- tank (HAC/PAH2) versions. The original challenge, which Involved having a basic vehicle strictly ldentlcol for both versions, Is being met. The modifications that were mode regarding handling qualities and tall shake are proving positive. There remains now for the flight test team the challenge of handling a new avlonle> update beginning with PT2"s first flight.

7 REFERENCES

(I) Dr. SCHYMANIETZ. J. lE BEL

«Tiger Development status Overv!ewn 17th EUROPEAN ROTORCRAFT FORUM, BERliN GERMANY, September 1991

(2) <(Engineering Design Handbook · Helicopter Performance Testing11 AMCP 706- 204.H.Q US. ARMY MATERIAl COMMAND

(3) P. HEGE, G. GENOUX

((The SARIS VIbration Absorbern

9th EUROPEAN ROTORCRAFT AND POWERED liFT AIRCRAFT FORUM STRESA. ITALY, September 1983

(4) G. SEITZ, T. KRYSINSKI

«<verview of Ttger Dynamics Validation Pfogrammn

48th ANNUAL FORUM OF THE AMERICAN HEliCOPTER SOCIETY, WASHINGTON, June 1992