Tweaks to OANS-BTV text

Changed some of the BTV explanation paragraph, some slight grammar  changes, added note about standard way to disengage btv.

docs/pilots-corner/a380x/a380x-advanced-guides/oans-btv.md

@@ -1,7 +1,7 @@
 # Onboard Airport Navigation System (OANS) & Brake To Vacate (BTV)
 
 Both the OANS (also known as Airport Navigation Function on the A350) and BTV add a high operational benefit to the A380,
-without them operations with optimal turnaround times and navigation on complex airports would be hardly possible.
+simplyfing navigation on complex airports and allowing optimal turnaround times.
 
 This advanced guide introduces the basic operation of the airport navigation function, the approaching runway advisory as
 well as setup and operation of BTV.
@@ -23,24 +23,24 @@ The OANS features a moving airport map on the flight crew's navigation display (
 AMDB database can be selected for display.
 
 On the ground at the departure airport, the airport map should be loaded automatically.
-Airports can always be selected manually through the OANS control panel, which can be opened via the arrow button on the lower
+Airports can be selected manually through the OANS control panel, which can be opened via the arrow button on the lower
 right of the ND. After selection of an airport, a click on "DISPLAY AIRPORT" loads the airport map.
 
 ![Select airport](../assets/advanced-guides/oans-btv/oans-cp-select-airport.png)
 
-The OANS airport map is active in ROSE NAV, ARC and PLAN EFIS mode. In PLAN mode, any airport of the database can be displayed.
-In all modes, the center of the map can be moved using the mouse (click and drag in the instrument).
+The OANS airport map is active in ROSE NAV, ARC and PLAN EFIS modes. In PLAN mode, any airport of the database can be displayed.
+In all modes, the center of the map can be moved using the mouse (click and drag in the navigation display).
 
 If you want to center the map on the aircraft again, double click on the map to open the context menu and select "CENTER ON ACFT".
 
 ![Center on ACFT](../assets/advanced-guides/oans-btv/oans-center-on-acft.png)
 
 ## Approaching Runway Advisory
 
-If the aircraft is on ground and ground speed is below 40 knots, OANS continuously checks the aircraft protection area
-in front of the aircraft (as widge as the wingspan, foresight of 7 seconds) for runways. When detecting a runway inside this
-area, an advisory is triggered on the PFD and ND. The advisory disappears, if the above conditions aren't met anymore, or
-the aircraft entered the runway.
+If the aircraft is on the ground and ground speed is below 40 knots, OANS continuously checks the aircraft protection area
+in front of the aircraft (as wide as the wingspan, projected 7 seconds ahead) for runways. When detecting a runway inside this
+area, an advisory is triggered on the PFD and ND. The advisory disappears when the above conditions aren't met anymore, or
+the aircraft has entered the runway.
 
 There is no aural warning (as RAAS).
 
@@ -53,8 +53,8 @@ the EFIS mode selector to PLAN, and load the destination airport using the OANS
 your destination airport, with the FMS landing runway marked with a green arrow in front of the runway identifier (QFU).
 Clicking on the runway identifier selects this runway for BTV.
 
-After selecting a runway, OANS displays two magenta lines projecting the required minimal stopping distance to DRY and WET
-conditions. The targeted exit should be chosen after the WET line only, to provide a safety margin. To finalize the
+After selecting a runway, OANS displays two magenta lines projecting the required minimal stopping distance for DRY and WET
+conditions. The targeted exit should be chosen after the WET line only, this provides a safety margin. To finalize the
 selection, the runway exit is selected by clicking on the corresponding label.
 The upper left of the ND now shows:
 
@@ -67,16 +67,14 @@ The upper left of the ND now shows:
 ![Runway + exit selected](../assets/advanced-guides/oans-btv/btv-setup-selected.png)
 
 To finalize the setup, the auto brake mode selector knob is turned to the "BTV" option, which arms BTV (this should be
-checked in the PFD's FMA).
+checked in the PFD FMA).
 
 ![Auto brake selector knob](../assets/advanced-guides/oans-btv/btv-abrk-selector.png)
 ![PFD FMA: BTV armed](../assets/advanced-guides/oans-btv/pfd-btv-armed.png)
 
 ## BTV operation after touchdown
 
-After touchdown of the main and nose wheel landing gears, BTV should now become active in the PFD's FMA. At first, BTV is
-going to use reversers (which of course have to be operated by the flight crew) to slow down the aircraft, then braking
-will become active at lower speeds. This is done to lower the brake temperatures, enabling a quicker turnaround.
+After touchdown of the main and nose wheels, BTV will become active and annunciated in the FMA. BTV monitors the decelleration of the aircraft with respect to the aircraft position and the exit selected and calculates when to start apply braking. Braking with BTV is quite different to standard autobrake modes, with BTV most of the braking happens very late in the landing roll and can be a bit disconcerting initially. This is done to minimise the energy absorbed by the brakes, lowering the brake temperatures and enabling a quicker turnaround.
 A green bar indicates the predicted stopping distance.
 
 ![OANS during rollout](../assets/advanced-guides/oans-btv/btv-active-stopbar.png)
@@ -86,6 +84,6 @@ BTV disarms, when one of these conditions apply:
 - The aircraft reaches the runway exit at the release speed of 10 knots
 - Flight crew applies a larger braking force through the pedals than BTV
 - Auto brake mode selector is turned to the DISARM position
-- A/THR instinctive disconnect push buttons (on the outside of the thrust levers) is pushed
+- A/THR instinctive disconnect push buttons (on the outside of the thrust levers) is pushed (This is the normal method of disarming, at 70kts groundspeed)
 
 For the last three conditions, the "AUTO BRK OFF" memo and aural callout will be triggered.