AIRBUS H125 / AS350B3e (2D Engine) Emergency Procedures

Question 1

DISCLAIMER

Answer 1

This flash card study aide is provided to ease and assist in studying much more comprehensive material provided by Eurocopter / Airbus. The creator of this study aide accepts no responsibility for inaccuracies or abbreviation of procedures. This is intended to introduce the associated material and all persons using these cards should study and reference the officially distributed material from the manufacturer. It is recommended that after referencing each card, the student should independently verify the information on that card by looking it up and learning the comprehensive information from the direct source. If any inaccuracies, misleading or typo errors are found, please notify the administrator of the study deck.

Question 2

FLAME OUT IN FLIGHT

SYMPTOMS

Answer 2

• Jerk in Yaw Axis (only in high power flight)
• Drop in Rotor RPM (Horn below 360 RPM)
• Torque at Zero
• NG Falling to Zero
• Generator Warning Light ON
• Engine Oil Pressure Warning Light ON
• ENTER AUTOROTATION!!

Question 3

AUTOROTATION

FORWARD FLIGHT

(Following Engine Failure)

Answer 3

AUTOROTATION PROCEDURE OVER LAND
1. Collective pitch: REDUCE to maintain NR in normal operating range.
2. IAS : Vy (65 kias).
- If relighting impossible or after loss of tail rotor thrust
3. Twist grip: IDLE position.
4. Maneuver the aircraft into the wind on final approach.
- At height about 70 ft (21 m)
5. Cyclic : FLARE.- At 20/25 ft (6/8 m) and at constant attitude
6. Collective pitch : GRADUALLY INCREASE to reduce the rate of descent and forward speed.
7. Cyclic : FORWARD to adopt a slightly nose-up landing attitude (< 10°).
8. Pedals : ADJUST to cancel any sideslip tendency.
9. Collective pitch : INCREASE to cushion touch-down.- At 20/25 ft (6/8 m) and at constant attitude
10. Cyclic, collective, pedals : ADJUST to control ground run.
- Once the aircraft has stopped
11. Collective pitch : FULL LOW PITCH.
12. Rotor brake : APPLY below 170 rotor rpm.

Question 4

AUTOROTATION

OVER WATER

Answer 4

Apply same procedure as over land, except items 10, 11 and 12, but maneuver to head the aircraft equally between the wind and wave direction on final approach. Ditch with minimum forward speed (IAS < 30 kt (56 km/h)) and rate of descent.

Then apply following check list for items 10, 11, 12.
- After touch-down
10. Collective pitch : MAINTAIN.
11 Doors jettison handles : PULL-UP.
12. Rotor brake : APPLY

Question 5

IGE HOVER AUTOROTATION

Answer 5

• Do Not Reduce Collective Pitch
• Control Yaw
• Cushion Touchdown by Increasing Collective
• Reduce Collective As Soon As Aircraft Is On The Ground

Question 6

OGE HOVER AUTO

Answer 6

• FULL LOW Collective Pitch
• When NR stops decreasing, forward Cyclic to Gain Airspeed (dependent on height above ground)
• Attempt Remaining Autorotation Steps

Question 7

RELIGHTING ENGINE IN FLIGHT

Answer 7

According to available height and cause of flame-out:
1. FUEL P / FUEL PUMP : ON

2. GENE : OFF
3. Starting selector : OFF, then ON position.

The relighting sequence will then run automatically as soon as N1 < 10 %.

• After relighting
  4. GENE : ON

FUEL P / FUEL PUMP : OFF.

At least 1000 ft (300 m) are necessary to complete relighting procedure after flame-out.

Question 8

TAIL ROTOR DRIVE FAILURE

Symptom

Answer 8

Will result in left yaw, extent will depend on power and speed at time of failure.

Question 9

TAIL ROTOR FAILURE

Hover IGE

Answer 9

LAND IMMEDIATELY

1. Twist Grip : IDLE position.
2. Collective : INCREASE to cushion touch-down.

Question 10

TAIL ROTOR FAILURE

Hover OGE

Answer 10

LAND AS SOON AS POSSIBLE

Simultaneously,
1. Collective : REDUCE depending on available
height.
2. Cyclic : FORWARD to gain speed.
3. Airspeed : MAINTAIN Vy or higher.
4. Collective : ADJUST to obtain minimum sideslip
angle.

If a go-around was performed, carry out an autorotative landing on an area suitable for the autorotation procedure.

Question 11

TAIL ROTOR FAILURE

In Cruise Flight

Answer 11

LAND AS SOON AS POSSIBLE

1. Airspeed : MAINTAIN Vy or higher.
2. Collective : ADJUST to obtain minimum sideslip angle.

On a suitable area for autorotative landing:

1. Twist grip : IDLE position.
2. Carry out an autorotative landing according to the autorotation procedure

(Refer to Section 3.2 § 1)

Question 12

LOSS OF TAIL ROTOR CONTROL

Answer 12

Symptom: jamming of pedals or loss of pedal effectiveness. These conditions make it impossible to change tail rotor thrust with the pedals.

WARNING: LANDING IS MADE EASIER WITH A RH WIND COMPONENT. WHEN AIRSPEED IS LESS THAN 20 KT GO-AROUND IS IMPOSSIBLE DUE TO LOSS OF VERTICAL FIN EFFICIENCY.

1. Cyclic and collective - ADJUST to set IAS to 70 kt (130 km/h) in level flight.
2. Hydraulic cut-off switch (collective grip) - OFF.
3. [ACCU TST] - PRESS for 2 sec. (load compensator depressurizes) On a suitable area for a running landing procedure: Make a shallow approach with a slight left sideslip. Perform a running landing. The sideslip will be reduced progressively as airspeed is reduced and collective is applied to cushion the landing.

Question 13

SMOKE IN CABIN

Source Not Identified

Answer 13

Heating, Demisting : OFF

(If smoke doesn’t clear)

1. [BATT] : EMER SHED
2. [GENE] : OFF.
3. [AVIONIC] (if fitted) : OFF.
4. Ventilate the cabin.

When smoke clears:

5. All consumers : OFF.
6. [BATT] : ON.
7. [GENE] : ON, check DC Parameters.

If smoke doesn’t clear

LAND AS SOON AS POSSIBLE

If smoke DOES clear, but;

If DC parameters not correct:

8. [GENE] : OFF.
9. Apply case A of GENE DC generator off line procedure.

LAND AS SOON AS PRACTICABLE

Smoke clears, and DC parameters correct

8. [AVIONIC] : ON.
9. Minimum required consumers : ON, one by one, if smoke returns, switch off that particular system for remainder of flight.

CONTINUE FLIGHT
depending on atmospheric conditions

CAUTION
When [EMER SHED] is actuated the VEMD goes off. Apply the procedure for failure of both screens (Section 3.5 § 1 VEMD screen failures).

Question 14

SMOKE IN CABIN

Source Identified

Answer 14

SOURCE IDENTIFIED

1. Corresponding system : OFF.
2. Ventilate the cabin.

CONTINUE FLIGHT
depending on system failed.

NOTE
After DC has been switched-off and on in flight, GOV light will remain on until the next normal full engine shut down and battery switch off on the ground

Question 15

VEMD SCREEN FAILURES

Answer 15

Failure of one screen

Failed Screen : OFF.
Read all available information on the other screen.
Informations are available using the [SCROLL] pushbutton either on the VEMD or on the collective grip.

If top screen fails, the 3-parameter engine page will be automatically displayed on lower screen but with torque and ΔNg off line. Only T4 and digital Ng will be available, refer to paragraph 4 for compliance with limitations.

Failure of both screens

To avoid any power overlimit, the maximum authorized power will be the power needed to establish level flight with the following law:

IAS kt = 100 kt at 0 Hp - (2 kt / 1000 ft).

LAND AS SOON AS PRACTICABLE
Landing procedure: Carry out a no hover landing.

Question 16

CAUTION MESSAGES ON VEMD

Answer 16

When a parameter is off line, the parameter value is not displayed on the corresponding VEMD screen and the parameter scale symbology is displayed in yellow.

Caution messages are self explanatory and the pilot shall comply with the action requested. If no light is lit on the caution and warning panel, no other action is required from the pilot.

IE: You get a VEMD message on shutdown “failure detected”, you may investigate, you may alert maintenance personnel, but it does not ground the helicopter unless an accompanying light such as GOV is illuminated. Message OVERLIMIT DETECTED do not conduct another flight until corrective Mx is conducted.

For all of these messages, unless otherwise required by accompanying caution/warning lights or procedures:
CONTINUE FLIGHT

Question 17

NR (ROTOR RPM) INDICATOR FAILURE

Answer 17

Maintain engine torque above 10%: NR reading is then given by the N2 pointer

LAND AS SOON AS PRACTICABLE

Question 18

N2 INDICATOR FAILURE

Answer 18

Check NR:

if it is normal with torque above 0%

CONTINUE FLIGHT

NOTE 1: The N2 value can be read on the VEMD screen. Press [SELECT], then [+] as many times as required to display the parameter in the rectangular window at the bottom of the FLI or 3-data screen.
NOTE 2: In case of Nf indication failure, the EBCAU may not be available.

Question 19

ABNORMAL N2 GOVERNING

Answer 19

Abnormal low NR and N2 (Parameters aligned)
FADEC governs N2 to a value that is significantly lower than usual.

This failure can be caused by an erroneous collective anticipator signal (XPC). NR/Nf values may decrease to 360 rpm before the failure is detected by the FADEC ( GOV comes on).
If NR/Nf drop below 375 rpm in flight:

1. Engine parameters : CHECK
2. NR/N2 : CHECK both parameters aligned

LAND AS SOON AS PRACTICABLE

Due to reduced tail rotor control margins avoid hover flights with left crosswind and carry out a no hover landing.

Question 20

Answer 20

Oil Temp Over °117c

Reduce power and set speed at 80 knots.

Temperature should fall rapidly; If not,

LAND AS SOON AS POSSIBLE

If temperature does decrease

LAND AS SOON AS PRACTICABLE
Check oil cooler fan operation

Question 21

OIL

IN FLIGHT

Answer 21

• Test Warning-Caution Panel and check that ENP P light illuminates
• If ENG P light is already on, or does not illuminate when tested (presume it is on):

LAND IMMEDIATELY: Autoration procedures apply; Shut down engine time permitting

• If ENG P light does illuminate when tested:
• LAND AS SOON AS PRACTICABLE.
• Monitor ENG P light

Question 22

Loss of N1, Torque or TOT parameters on VEMD

Answer 22

When a parameter is off line, the parameter value is not displayed on the VEMD upper screen and the parameter scale symbology is displayed in yellow.

The First Limitation Indicator (FLI) is replaced by the 3 data symbology (Ng/delta Ng, t4 and torque) and a failure message is displayed.

Question 23

N1 INDICATOR FAILURE

Answer 23

LAND AS SOON AS PRACTICABLE

Comply with the maximum TRQ value and TOT limit of 842°C.

NOTE

In this case, the TOT limitations displayed are the starting limitations.
An engine overlimit may be recorded and the OVERLIMIT DETECTED message displayed on VEMD if the TOT exceeds 750°C. The over limit can be ignored

Question 24

TORQUEMETER FAILURE

Answer 24

LAND AS SOON AS PRACTICABLE

Question 25

N1 AND Tq indications failure

Answer 25

**LAND AS SOON AS PRACTICABLE** ## Footnote The VEMD switches to 3-data symbology with only TOT and numerical N1 as valid parameters. Comply with N1 limitations in the above table, and respect a TOT limit of 842°C.

Question 26

TOT INDICATOR FAILURE

Answer 26

**LAND AS SOON AS PRACTICABLE** • TOT Indicator Failure: Comply with N1 and TRQ limitations. Switch off heating and demisting system. **On ground: do not start the engine**

Question 27

IN FLIGHT

Answer 27

* [GEN] or [GENE] : **OFF** * CWP : **MONITOR for BATTERY TEMP** * **[GENE RESET]** **LAND AS SOON AS PRACTICABLE** **CAUTION** If the battery fails, the VEMD will go out and only the analogue NR indication will remain. Apply the procedure for failure of both screens (Section 3.5 § 1 VEMD screen failures).

Question 28

IN FLIGHT

Answer 28

* U/BUS voltage : **MONITOR** ## Footnote **CONTINUE FLIGHT**

Question 29

IN FLIGHT

Answer 29

* Reset GEN, if it then produces 26V or more; **CONTINUE FLIGHT** * If reset unsuccessful; **LAND AS SOON AS PRACTICABLE** **NOTE** Probable cause of such a failure is a generator defect that does not make GENE come on

Question 30

IN FLIGHT

Answer 30

* Unnecessary equipment : **OFF** * *CONTINUE FLIGHT** * *NOTE** After engine starting on battery, a temporary high generator current is normal because the battery is being recharged. During this phase, avoid using high electrical load consumers

Question 31

DURING START

Answer 31

1. Engine starting selector : **OFF position** 2. Emergency fuel shut-off handle : **AFT** 3. [FUEL P] : **OFF** 4. [CRANK] : **PRESS (10 sec.)** 5. [EMER SW] : **OFF** 6. Rotor brake : **APPLY (below 170 rpm)** 7. **Evacuate aircraft and fight fire from outside**

Question 32

Hover, Takeoff, Final

Answer 32

**LAND IMMEDIATELY** ## Footnote Carry out a no hover powered landing. Once on ground, apply same procedure as above.

Question 33

IN FLIGHT

Answer 33

**LAND IMMEDIATELY** ## Footnote 1. Collective : **LOWER** 2. IAS : **Vy** 3. Autorotation procedure : **APPLY** 4. Emergency fuel shut-off handle : **AFT** 5. [FUEL P] : **CHECK OFF** 6. Engine starting selector : **OFF position** - After Landing: 7. [EMER SW] : **OFF** 8. Rotor brake : **APPLY (below 170 rpm)** 9. **Evacuate aircraft and fight fire from outside**

Question 34

ON START UP

Answer 34

Engine starting selector : **OFF position immediately**

Question 35

IN FLIGHT

Answer 35

1. Flight parameters : **CHECK** Emergency mode automatically self-engages GOV illuminates. 2. Collective : **AVOID abrupt changes** Maintain Ng \> 80% Hp \< 20000 ft (6096 m) Maintain Ng \> 85% Hp ›20000 ft (6096 m) **LAND AS SOON AS PRACTICABLE** Approach and Landing: . Make a powered approach . Avoid steep angle . Collective : **SLOWLY down to low pitch**. Engine starting selector : **OFF** NOTE On VEHICLE page: FF and END . This failure can also result in loss of delta Ng and torque parameters on the VEMD.

Question 36

Flashing at idle or during starting or shutdown

Answer 36

Governor redundancy failure, no impact on governing function. ## Footnote . Start-up procedure: Abort, refer to Maintenance Manual . Autorotation training: Cancel training, return to base

Question 37

IN FLIGHT

Answer 37

**Continuously on:** Governing function degraded 1. Collective : **AVOID abrupt power changes** 2. IAS : **MAINTAIN below VNE power off** **LAND AS SOON AS PRACTICABLE** **On ground: Do not start engine**

Question 38

IN FLIGHT

Answer 38

Check engine oil pressure, if pressure is low, or zero, **LAND IMMEDIATELY** Autorotation procedures apply. Shut down engine time permitting If engine oil pressure ok, **LAND AS SOON AS PRACTICABLE**

Question 39

IN FLIGHT

Answer 39

Twist grip : **TURN to FLIGHT position** **CONTINUE FLIGHT**

Question 40

IN FLIGHT

Answer 40

**LAND AS SOON AS POSSIBLE** * *REDUCE power** * *Low power approach and landing** * *Be prepared in case of a loss of engine power.** NOTE Takeoff is prohibited until checks specified in TURBOMECA Maintenance Manual have been completed

Question 41

IN FLIGHT

Answer 41

Reduce Power **LAND AS SOON AS POSSIBLE** Main Gear Box low oil pressure \< 1 bar If a safe landing is not possible, continue flight to the nearest appropriate landing site, reduce power to fly at minimum power speed (Vy). **NOTE** **At low power (Vy) a maximum of 55 min. of simulated flight time has been demonstrated during bench tests**

Question 42

IN FLIGHT

Answer 42

Slow to Vy (65 KIAS), if light goes out **LAND AS SOON AS PRACTICABLE** if light stays on **LAND AS SOON AS POSSIBLE**

Question 43

IN FLIGHT

Answer 43

**LAND AS SOON AS POSSIBLE** Reduce Power Monitor MGB P and MGB TEMP

Question 44

IN FLIGHT

Answer 44

**CONTINUE FLIGHT** Avoid prolonged hovering

Question 45

IN FLIGHT

Answer 45

**LAND AS SOON AS PRACTICABLE** For all cases, normal approach and landing **LOSS OF HYDRAULIC PRESSURE (Less than 30 bar) on corresponding circuit** (Accompanied by GONG) **CAUTION** During high load factor maneuvers, servocontrol reversibility may be encountered Keep aircraft in a more or less level attitude. Avoid abrupt maneuvers. Maintain angle of bank less than 30°. Maintain IAS below 110 kt (or VNE if less). **NOTE** One remaining circuit allows continued safe flight and landing. If HYD1, loss of LH circuit, may also get LIMIT light If HYD2, loss of RH circuit: Tail rotor control hydraulic power lost. **CAUTION** Do not press the [ACCU TST] pushbutton as this would discharge the yaw load compensator and right pedal loads may be significant

Question 46

IN FLIGHT

Answer 46

Disconnected for lead acid. If illuminated, possible wire short should be investigated. Normal EP is: If ABOVE U max 1. [BAT/EPU] : **ON** 2. [GENE] : **OFF** 3. Unnecessary equipment : **OFF** **LAND AS SOON AS PRACTICABLE**

Question 47

Answer 47

Check that battery button is ON If ON but bad V **LAND AS SOON AS PRACTICABLE** If V good **CONTINUE FLIGHT**

Question 48

IN FLIGHT

Answer 48

* U bus on VEMD : **CHECK** * [GENE] : **CHECK ON**, if it IS: * "GENE RST" : **Circuit breaker check if popped** * If light goes out **CONTINUE FLIGHT** * If light remains on * [GENE] : **RST** * [GENE] : **ON** If light goes out **CONTINUE FLIGHT** If light stays on: * Unnecessary equipment : **OFF** * U bus on VEMD : **MONITOR** **LAND AS SOON AS PRACTICABLE** **CAUTION** If the battery fails, the VEMD will go out and only the analogue NR indication will remain. Apply the procedure for failure of both screens (Section 3.5 § 1 VEMD screen failures).

Question 49

IN FLIGHT

Answer 49

* CHECK [INV] ON * If On but Loss of all AC consumers NOTE AFCS\* disengages automatically INV Controls **: HANDS ON** **CONTINUE FLIGHT**

Question 50

Answer 50

**LAND AS SOON AS POSSIBLE** Avoid large attitude changes Remaining fuel approx. 15.8 Gal Approx. 15 minutes flying time at MCP WARNING AVOID LARGE ATTITUDE CHANGES AS THIS COULD LEAD TO AN ENGINE FLAME-OUT.

Question 51

IN FLIGHT

Answer 51

**LAND AS SOON AS POSSIBLE** 1. Collective : **REDUCE POWER** 2. [FUEL P] or [FUEL PUMP] : **ON** Low power approach and landing * *WARNING** * *BE PREPARED IN CASE OF AN ENGINE FLAME-OUT**

Question 52

IN FLIGHT

Answer 52

**Fuel filter pre-clogged** Fuel filter pre-clogging level 2 reached **WARNING** FUEL FILTER BY-PASS OPENING LEADS TO CONTAMINATION OF THE FUEL LINES AND THE GOVERNOR, WHICH MAY INDUCE N1 OSCILLATIONS, LIMITED POWER OR POSSIBLY FLAME-OUT. **LAND AS SOON AS PRACTICABLE** **MONITOR N1 If N1 oscillations occur:** **LAND IMMEDIATELY**

Question 53

Flashing at idle or during starting or shutdown

Answer 53

Fuel filter pre-clogging level 1 reached • One flight of 3 hours maximum flight time can be performed before maintenance action

Question 54

Answer 54

Check pitot button ON Monitor airspeed indicator CONTINUE FLIGHT

Question 55

Answer 55

Push horn button **ON** ## Footnote **CONTINUE FLIGHT**

Question 56

IN FLIGHT

Answer 56

Reduce airspeed (70 knots maximum) **LAND AS SOON AS PRACTICABLE** Descent and approach at low rate of descent

Question 57

IN FLIGHT

Answer 57

**CONTINUE FLIGHT** NOTE The forward reading lights can be used as additional instrument panel lighting.

Question 58

FLIGHT CONTROL HARDOVER OR SERVOJAM On Takeoff, HIGE, Final (Hydraulics)

Answer 58

* *(if immediate landing is possible)** * *LAND IMMEDIATELY** After landing: 1. Hydraulic cut-off switch (collective pitch) : OFF 2. Engine and rotor shut down procedure : APPLY

Question 59

FLIGHT CONTROL HARDOVER OR SERVOJAM IN FLIGHT (Hydraulics)

Answer 59

1. IAS : SET to between 40 and 60 kt, Enter sideslip if necessary 2. Hydraulic cut-off switch (collective pitch) : OFF, apply HYDR procedure * *LAND AS SOON AS POSSIBLE** * *NOTE** With no hydraulic pressure, the aerodynamic loads to be counteracted may be heavy at high airspeed: - Collective pitch: up to 45 lbf to pull, - Cyclic: 16 to 27 lbf to push left, - Cyclic: 4.5 to 9 lbf to push forward.

Question 60

BLEED VALVE FAILURE

Answer 60

When the bleed valve opens, a flag appears on the FLI or 3-data page. The flag disappears when the bleed valve closes. The bleed valve is normally open when the engine is shut down, during starting and at low power settings. - If the flag does not disappear at high power settings (i.e. near MCP or above), the maximum available engine power is reduced, specifically in cold weather. - If the flag does not reappear at low power settings, the engine may surge. Avoid abrupt changes in power settings. - Bleed valve failure results in **GOV**. LAND AS SOON AS PRACTICABLE

Question 61

IN FLIGHT

Answer 61

Main servo unit max. load reached In high speed cruise flight or steep maneuvers: 1. Collective : **Reduce power.** 2. Cyclic : **Reduce speed or load factor.** * *CONTINUE FLIGHT** * *NOTE** LIMIT may appear associated with HYD1 in case of hydraulic failure

Question 62

IN FLIGHT

Answer 62

**LAND AS SOON AS PRACTICABLE** ## Footnote Jamming of a distributor valve on main servo unit

Question 63

YAW SERVO-CONTROL SLIDE -VALVE SEIZURE (Hydraulics)

Answer 63

**In Hover**: If no movement about the yaw axis, LAND NORMALLY If rotating about the yaw axis, cut off hydraulic actuator on collective **In Cruise Flight**: REDUCE IAS to between 40 and 60 kt (74 and 111 km/h) in level flight, enter sideslip if necessary. Hydraulic cut-off switch (collective pitch): OFF

Question 64

ROTOR BRAKE FAILURE

Answer 64

WARNING ## Footnote WAIT UNTIL ROTOR COMES TO A STANDSTILL BEFORE LEAVING THE AIRCRAFT. Rotor stopping with wind blowing: 1. Aircraft : **INTO WIND** 2. Cyclic stick : **Slightly INTO WIND**

Question 65

ICS FAILURE

Answer 65

1. ICS : **OFF** 2. COM 1 : **Check ON, adjust volume** NOTE 1 VHF communications will remain available for the RH pilot only via COM 1 transceiver. Audio warnings will be transmitted via the COM 1 audio system. NOTE 2 **Abort or cancel hoisting operations in case of ICS failure.**

Question 66

LIST OF FUNCTION WHICH MUST REMAIN ON WHEN FLYING ON BATTERY ONLY

Answer 66

***DAY*** * Battery * Fuel Pumps * VHF * Radio-Nav ***NIGHT*** * Day equipment plus: * Instrument lighting * Attitude Indicator * Position Lights * Anticollision lights

Question 67

HORN ACTION CONTINOUS

Answer 67

**REDUCE COLLECTIVE PITCH!** Reduce speed and level If hydraulic light on, use HYDRAULIC OUT EP If down collective shuts off horn then the malfunction is low rotor RPM, usually engine failure Check engine parameters by applying collective pitch very gradually

Question 68

HORN ACTION INTERMITTENT

Answer 68

NR is above 410 RPM: Slightly increase collective pitch in order not to exceed 430 RPM (Recuce cyclic back pressure if applicable)

Question 69

HORN AUDIO WARNINGS

Answer 69

**GONG**: A gong is generated each time a RED warning appears on the warning panel. **CONTINUOUS TONE**: Two tones can be heard: When NR is below 360 rpm When take-off limitations are exceeded After a 1.5 sec. delay if power remains within transient limitations. Immediately when transient power limitations are or may be exceeded during fast power increases. **INTERMITTENT TONE**: An intermittent tone is heard when the NR is above 410 rpm.