AboutD. Norkus Expertise I can address questions about airline pilot employment & entry level airline careers in the United States, women pilots, flight training, pilot certification, U.S. flight scholarships (mostly for women), aviation & airline safety topics, aviation accident investigation and airline operations.
***Please note, I cannot address flight training & career queries from outside the United States, or aero engineering degree programs/careers, aviation management topics. ****
Experience U.S. Regional Airline Pilot. I have also had 15 years previous experience in airline ground operations, as well as a part 91 commercial skydive pilot and ferry pilot.
Organizations International Organization of Women Pilots, Women In Aviation International, Aircraft Owners & Pilots Organization, Air Line Pilots Association
Question Dottie,
Thanks for the help on my last question. The AOPA website has a lot of good things to look at. I needed clarification on somethings I have been seeing on appoach charts and radar instrument approach minimums airport listings.
1) What does HAT/HAA on the approach minimums stand for?
2) When it says MDA 2800/Vis 24, does this mean at 2800 feet if you don't see the ruway you execute a missed approach? And what does the "Vis 24" mean?
3) Would you please explain the Categories A,B,C, and D aircraft.
4) Finally, could you briefly explain RVR and what bearing that has on your decision to take-off.
Thanks for your help.
Dan
Answer Dan
1) What does HAT/HAA on the approach minimums stand for?
"Height Above Threshold"/"Height Above Airport"
2) When it says MDA 2800/Vis 24, does this mean at 2800 feet if you don't see the runway you execute a missed approach? And what does the "Vis 24" mean?
Using that format above, I am guessing you are looking at a NOS Approach Chart. It's been ages since I have used one as the airlines all use Jeppesen (and they are tailored manuals for each company). That said, and not having seen the chart, I believe that format reads as a Minimum Descent Altitude of 2,800ft with a required RVR of 2,400 ft. A pilot would fly at the MDA of 2,800 ft until reaching the MAP/Missed Approach Point, not go missed as soon as reaching that altitude with no visual as the MAP may be a distance away after leveling off at the MDA. The visibility required to shoot the approach is 2400ft. General aviation is Part 91 and has no restrictions like the airlines. It can be zero/zero and they can still try the approach. Each operator determines how the minima applies to them. Interestingly enough, the only controlling factor for the airlines is visibility. The approach can have a DH or MDA that is above the reported ceiling, yet they can still shoot the approach if the visibility is equal to or greater than the published VIS minima.
Here are some good links that explain how to read approach plates (most sites use NOS as they are flight sim sites and NOS are cheap to buy):
3) Would you please explain the Categories A,B,C, and D aircraft.
"Approach categories" for aircraft are determined by multiplying the stall speed of the aircraft in a landing configuration by 1.3. Category A Aircraft are <90 knots approach speed, Category B Aircraft 90-120 knots and Category C-E Aircraft are 120> knot approach speed aircraft.
4) Finally, could you briefly explain RVR and what bearing that has on your decision to take-off.
Depending on the weather, there may be no takeoff. Under Federal Aviation Regulations Part 121 that govern the airlines (specifically §121.651 - Takeoff and landing weather minimums) a flight cannot take off unless the weather is at least the visibility required by the "operations specifications" of that airline for that runway. Quite often, this is the same as the "Take Off Minimums" presecribed for that airport on the airport diagram but not always.
Runway visual range is measured by transmissometers set up along the side of the runway that determine visibility between the towers quite accurately. There are touchdown, mid-field and roll out reporting transmissometers. For example an airline flight wanting to take off may need the three transmissometers to be reporting at least 600 ft in each sector to legally take off. "RVR 600/600/600". Anything less and they must wait for the weather to improve.
Additionally, when the weather is less than the minima required for the approach to return to the airport (in case of an engine failure), there must be a takeoff alternate on the flight plan:
§121.617 - Alternate airport for departure
(a) If the weather conditions at the airport of takeoff are below the landing minimums in the certificate holder's operations specifications for that airport, no person may dispatch or release an aircraft from that airport unless the dispatch or flight release specifies an alternate airport located within the following distances from the airport of takeoff:
(1) Aircraft having two engines. Not more than one hour from the departure airport at normal cruising speed in still air with one engine inoperative.
(2) Aircraft having three or more engines. Not more than two hours from the departure airport at normal cruising speed in still air with one engine inoperative.
