my coworkers always look at me funny when i take up an intercept heading following departure in order to intercept the direct track from the departure airport and the first fix in the clearance
the vast majority of pilots just punch in DTO the first fix as soon as they are ready to proceed enroute
i admit that sometimes the difference in track is negligible but in examples like yours the difference can be critical
"Radar identified, cleared on course".
"Cleared to the XYZ airport, flight planned route".
Seems pretty simple to me.
cpl_atc said that the protected airspace is 10 nm of direct track for GPS equiped.
If I'm in my plane, with no GPS and in range from XYZ, my protected airspace is supposed to be much bigger. As said in earlier post, ATC doesn't seem to read your equipment code, so they don't know you don't have GPS, are they automatically give you 10 NM because they "assume" you're GPS equipped? I've been cleared direct from 150 nm before on a TACAN and yes, I bet I was more than 10 NM from the actual direct track.
Hit the DTO button and go.AuxBatOn wrote:I meant let's says ATC says "cleared direct XYZ"
Tell ATC, we are unable direct, requesting vectors or on course FPR.AuxBatOn wrote:If I'm in my plane, with no GPS
If you accept the clearance, you better be able to do it. If not, tell them "unable".AuxBatOn wrote:I've been cleared direct from 150 nm before on a TACAN and yes, I bet I was more than 10 NM from the actual direct track.
first, I can't hit DTO Enter
Second, yes you are able direct, you receive the station (didn't I tell you we were in range?) So I can accept.
Third, direct implies great circle on ATC screens. Well, we work in Magnetic in the airplane. 150 NM away, the magnetic variation is different that the mag var where I am. The TACAN emits radials, in degree magnetic from where the station is. My kit (any kit), translates that into a steering to take with the magnetic variation where you are. So, I fly a steering to the station that is 3-4 degrees off (150 NM away that's about 10 NM off the track ATC expects us to fly), even though I fly an accurate track to the station. As I get closer, I can actually see the track to take changing. Now, we have an INS which is NOT IFR certified but that is dead accurate. If I punch in the coordinates of the TACAN station, I can actually see, 150 NM away, that the station representation on my digital map is 10-20 miles off to the south of the station. It happens on any aircraft, people just don't realize it because they don't have a depiction of where the kit thinks the station is.. This is WHY the protected airspace on conventional DIRECT is larger...
It doesn't matter if the pilot "thinks" ATC is watching our every move and basing sep on that - sometimes they actually expect you to go either PP direct or ON COURSE. Sometimes they do watch your every move - sometimes they DON'T! At those spacing intervals there is very little room for error.
The post was aimed more at the boys with the fancy gear that think it's okay to go PP direct as opposed to "on course".
If in doubt check it out....or If in doubt chicken out.
Unless I've missed what you are saying, this is correct. I've used GPS and INS, LORAN, the good ol VOR and NDB and it has been the same in every case. I can't see the Tacan being any different. The only question I have is do you have a track bar or a needle indicating you are on or off course?
Actually, domestically, the spacing between aircraft using conventional navaids is much less then the required separation for aircraft using GPS direct tracks. (Non-radar separation, that is. On radar 5 miles is 5 miles, regardless of what the aircraft are navigating with.)Bookem Lou wrote:Just one last thing I want to point out. The reason that there is bigger spacing between aircraft using conventional navaids like VOR and NDB is that the conventional navaids are less accurate than GPS, not because there is ambiguity as to where the aircraft (or the station) is. When you figure GPS is precise to within 10 feet and a VOR on its own can't place you guaranteed within 1 mile over better than 100 miles more than 50% of the time. The slight movement of your HSI track bar could be hundreds or thousands of feet of lateral movement the further you get, a significant amount when we're placing aircraft within 5 miles of each other on occasion.
The protected airspace (tolerance + separation + error factor) air traffic control uses for an aircraft operating between two conventional navaids is: 4 miles (4.34 miles if NDB) either side of the centerline to a distance of 51 miles (50 if NDB), then expanding outward within lines that diverge at 4.5 degrees (5 if NDB) until meeting similar lines from the next navaid.
The protected airspace (tolerance + separation + error factor) for GPS directs (and RNAV directs within adequate signal coverage) is 10 miles either side of the centerline.
Again, this is all for NON RADAR separation. On radar, 5 miles (or 3 in certain places) between targets is the separation standard.
Direct point to point using standard equipment, (/S on the flight plan) outside of signal coverge of a navaid or while not on an airway, your protected airspace is 45nM either side of track.AuxBatOn wrote:Thanks, but I knew for the airways. I was wondering off airways. But I guess on Radar it doesn't make a difference from what I understand? You need to maintain 5NM so if you clear me direct YQT for example, you'll keep an eye on me and that would be the end?
This is only non-radar. If you are within radar and frequency coverage (controllers must have direct controller pilot communication to use radar standards) then we only protect 5nM regardless of the equipment onboard the aircraft since we are using our equipment (radar) rather than position reports from the pilot/aircraft to determine separation.
On an other note, do you guys read the equipment code before clearing someone direct? I have been cleared NUMEROUS times direct from 300 nm away from a station and everytime, as you said, I would come back "Unable direct request initial vector"? We are not S (we do not have ADFs), but we are VOLUT. Maybe the fact that we usually cruise into or above RVSM makes controllers think we are RNAV equiped...
Exactly right, we'll keep an eye on you on radar and if you start getting too close to other traffic, we'll put you on a heading to ensure an accurate track until after the traffic is clear.AuxBatOn wrote:Thanks, but I knew for the airways. I was wondering off airways. But I guess on Radar it doesn't make a difference from what I understand? You need to maintain 5NM so if you clear me direct YQT for example, you'll keep an eye on me and that would be the end?
And it doesn't matter if there is an airway there or not, the numbers I mentioned above can be used any time an aircraft is navigating to or from a navaid. So if you are given PP direct a navaid, those numbers still apply.
Which equipment suffixes do you file as, and are you RVSM certified?AuxBatOn wrote:On an other note, do you guys read the equipment code before clearing someone direct? I have been cleared NUMEROUS times direct from 300 nm away from a station and everytime, as you said, I would come back "Unable direct request initial vector"? We are not S (we do not have ADFs), but we are VOLUT. Maybe the fact that we usually cruise into or above RVSM makes controllers think we are RNAV equiped...