> For the complete documentation index, see [llms.txt](https://bell-505-guide.gitbook.io/bell-505-maintenance-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bell-505-guide.gitbook.io/bell-505-maintenance-guide/line-maintenance/removal-installation/main-rotor/installing-the-nr-sensor.md).

# Installing the NR sensor

## Preliminary requirements

### Consumables, materials and expendables

| Name     | Identification/References                          | Quantity |
| -------- | -------------------------------------------------- | -------- |
| Lockwire | [C-508](https://www.bellhelicopter.net/tp/#/C-508) | AR       |

### Safety conditions

{% hint style="danger" %}
Obey all the safety precautions when you do maintenance on or near electrical/electronic equipment. If you do not obey these precautions, injury to personnel and/or damage to equipment can occur ([BHT-ELEC-SPM](https://www.bellhelicopter.net/tp/toc/505/ELEC-SPM), Chapter 2).
{% endhint %}

{% hint style="warning" %}
Make sure not to pull on the cables too much to prevent damage to the cables and connectors.
{% endhint %}

{% hint style="info" %}
When torque is used in a step but there is no specific torque value, refer to the [BHT-ALL-SPM](https://www.bellhelicopter.net/tp/toc/505/SPM), Chapter 2 to find the correct torque value.
{% endhint %}

## Procedure

1. Remove the protective caps and plugs from the NR sensor (6241SU4) and the port of the transmission pump adapter.
2. Make sure that the part of the shaft that is not-slotted is aligned with the port of the transmission pump adapter.

{% hint style="info" %}
There are 24 threads per inch (25.4 mm) on the threaded part of the NR sensor (6241SU4). The NR sensor (6241SU4) moves 0.042 inch (1.07 mm) for one turn.
{% endhint %}

3. Put the NR sensor (6241SU4) in the transmission pump adapter and turn it carefully until it lightly touches the shaft, then loosen it one turn. There must be a gap of 0.040 to 0.060 inch (1.02 to 1.52 mm) between the point of the NR sensor (6241SU4) and the part of the shaft that is not-slotted.
4. Torque the nut 95 to 105 inch-pounds (10.7 to 12 Nm).
5. Safety the nut with Lockwire (C-508).
6. Remove the protective caps or plugs from the connectors.
7. Connect the connector (6241SU4J1) to the connector (6241SU4P1).
8. Install the screw, washers, clamp, spacer, and nut on the connector (6241SU4J1) and the truss assembly.
9. Torque the nut.

## Requirements after job completion

### Required Conditions

<table><thead><tr><th>Action/Condition</th><th data-type="content-ref">Reference</th></tr></thead><tbody><tr><td>Install the upper-left mid-fuselage access-panel (433AL).</td><td></td></tr><tr><td>Install the left transmission fairing (432AL).</td><td></td></tr></tbody></table>


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