1. All Weather Takeoff and Landing
HPA Group
Brett Mather
Ryan Beach

2. Requirements Technology
All weather takeoff and landing is broken up into the following sections:
Requirements
Technology

3. All-Weather Terminal Area (ATWA) Operations
Basic Types of AWTA approach and landing operations
Visual Approach
Aircraft is being operated in normal visual flight rules (VFR) and normal instrument flight rules (IFR)
Instrument Approach
Instrument approach procedures permit descent in IFR conditions to allow for a safe landing.
Standard instrument approaches include International Civil Aviation Organization (ICAO), standard Navigation Aids (ILS, MLS, VOR, VOR/DME, NDB), as well as approaches based on ATC radar services.

4. All-Weather Terminal Area (ATWA) Operations (cont’d)
Requirements for VFR (FAR Part )
Regardless of ATC clearance, no pilot may takeoff or land when the reported ceiling and visibility is less than:
Day Operation: 1,000 ft ceiling and 1 mile visibility
Night Operation: 1,000 ft ceiling and 2 mile visibility
Where local surface visibility restrictions exist (smoke, dust, blowing snow, etc.) the visibility for day and night operations may be reduced to ½ mile provided all flight beyond 1 mile from the airport can be accomplished outside of the surface visibility restriction.

5. All-Weather Terminal Area (ATWA) Operations (cont’d)
Requirements for IFR (FAR Part )
Prior to takeoff, the pilot must obtain ATC clearance and must pass weather conditions specified in operation specifications manual take-off minimums.
Prior to the final approach segment of the instrument approach, the destination airport must issue a weather report with above-minimum weather conditions for the pilot to pass the final approach fix.
If the pilot has entered the approach and an updated weather with below-minimum weather conditions, the pilot may continue until decision height.
At the DH, the pilot may continue to touch down if:
A normal touchdown will occur within the touchdown zone.
The flight visibility agrees with the instrument approach procedure being used
In a category I approach, one of the following visual references must be identified:

6. All-Weather Terminal Area (ATWA) Operations (cont’d)
Requirements for IFR (FAR Part ) (cont’d)
The approach light system
The touchdown zone or touchdown zone markings
The touchdown zone lights
The runway or runway markings
The runway lights
The threshold
The threshold markings
The threshold lights
The runway end identifier lights
The visual approach slope indicator

7. Decision Height (DH, ft.) Runway Visual Range (RVR, ft.)
All-Weather Terminal Area (ATWA) Operations (cont’d)
Categories of Instrument Approach Procedures
Category
Decision Height (DH, ft.)
Runway Visual Range (RVR, ft.)
Alert Height (AH, ft.)
Equipment allowed
CAT I
DH > 200
RVR > 1800
N/A
CAT II
200 > DH > 100
RVR > 1200
CAT IIIa
100 > DH
RVR > 700
100
Fail-passive & fail-operational
CAT IIIb
50 > DH
700 > RVR > 150
Fail-operational
CAT IIIc
CAT IIIc landing has no limit on DH and RVR, but is currently unauthorized

8. Landing Requirements (military)

9. Technologies for All Weather Takeoff and Landing
Aircraft Design
Electronics
Runway Design

10. Aircraft Design Stronger landing gear for rough landings
Landing gear swivel
First used on Boeing to accomplish tighter turns on the ramp but is consistently used for crosswind landings
Better tire design
Brighter aircraft lights with upgraded high intensity discharge (HID) bulbs
Example design problem associated with weather: Tail Dragger aircraft taxiing in a strong cross wind can cause the plane to weathervane due to the light weight tail with small force on the tail wheel.
Michelin Tire Design

11. Electronics Air Traffic control (ATC)
Better weather prediction and detailed weather reports
Pilots must be informed of landing conditions (wind speed/direction, runway surface conditions)
Auto-pilot can execute landings in conditions of poor visibility that would be impossible otherwise
Sophisticated systems can also execute landings in severe crosswind conditions
Technology to improve visibility
Fog defeating system converts signals from on-board sensors and airport navigational aids into a holographic image of the approaching runway, which is projected onto a glass screen between the pilot and the windshield.

12. Friction Measurement / Testing Device
Runway Design
Rain Snow/ice landing
Wet and icy runways are the leading cause of landing accidents worldwide
NASA Joint Winter Runway Friction Measurement Program developed for braking tests for aircraft and friction measurement ground vehicles in the U.S. and Canada
Landing Surface Quality Evaluation
Visual inspection to determine the type of contaminant (rain, snow, etc) and the extent of its coverage
Thickness of contaminant
Friction Measurement
Lighting Systems (brightness can often be controlled by the pilot)
Chemical treatment for snow and ice (FPD (freezing point depressant)
Better runway surface (Grooved runway reduce hydroplaning based on research from NASA in 1968)
Some surfaces designed to retain anti icing chemicals
Grooved Runway
Friction Measurement / Testing Device

13. Runway Design / Electronics
ISL (instrument landing system)
Primarily consists of two subsystems: one for lateral guidance (Localizer), one for vertical guidance (Glideslope or GlidePath)
Marker beacons are used to measure how far until landing
All of these systems emit signals at different frequencies that are translated by electronics to determine the position of the aircraft
ILS Localizer
ILS Localizer

14. Runway Design / Electronics
MLS (Microwave landing system)
Microwave landing system are all weather landing systems that are similar to ILS.
Fewer transmitter stations needed for MLS (usually a single box)
Approach Azimuth station, Elevation station, and Range Station
MLS Elevation
Azimuth Measurement Range

15. Electronics
WAAS / GPS (Wide Area Augmentation System / Global Positioning System
WAAS is a system that improves the accuracy of GPS from the original 4-20 meter accuracy to a 2-3 meter accuracy by removing error cause by the earths ionosphere
This system basically ended the development of MLS
Normal GPS is not accurate enough to land a plane but with WAAS capability it is now possible.
New techniques such as Differential GPS can be even more accurate (calibrates GPS by measuring known fixed locations)

16. Questions?

17. References