Descend rate on final

[Poseidon]

Hi, is there som eformula to define my descending rate during final approach as a result of ground speed, altitude and distance from the runway?

Ok we say that 700 FPM is the ideal for a 737 (for example) but flying IFR plan with final VFR landing, sometimes they give me clearance in 3000 ft and 7 miles from the runway and other times 2200 ft and 8 miles from the runway.

I could also define a formula myself (using some trigonometry) but I am not sure about the concept of ground speed. Is it the projection of speed on the ground or it is just ignoring the air resistance? In the second case even if the air resistance is ignored and the indicated airspeed is constant, the ground speed would inscrease when descending because the descending path is longer than a straight one.

Thanks for any help.

[packercolinl]

There are any number of variables that are going to affect your approach. All have to be factored in to acheive a good landing.

FS provides some information in the introductory pages
for various aircraft and once you know the aircraft you are flying you won't have any problems.

It is practice and more practice like anything else. Pick an aircraft you like and learn to fly it. Find out its capabilities and use it til you know it backwards.

And yes you can and should be doing the mental calc. once you know the aircraft so you can respond appropriately to to ATC instructions

Cheers.

[OTTOL]

Ok we say that 700 FPM is the ideal for a 737 (for example) but flying IFR plan with final VFR landing, sometimes they give me clearance in 3000 ft and 7 miles from the runway and other times 2200 ft and 8 miles from the runway.

You're talking about two different things here. (1) Descent Rate   (2)ATC assigned altitude        Once you are on profile(an imaginary line extending upward from the approach end of the runway at 3.5 degrees) You can use an ILS, a visual indicator(VASI/PAPI) or just plain old unguided visual descent. The rate required can be quickly determined by taking the airpseed, halving it and adding a zero. IE: 120kts   120/2=60  (60 add a zero)    =600fpm             The altitudes you mentioned are assigned in accordance with terrain, the applicable approach(whether you are IFR or not), noise abatement, approach corridors for other airports or any of a number of other factors.   To bring these two together: usually you would be assigned an intercept altitude and once you join the glideslope or VASI, use the descent rate previously mentioned, to maintain a proper descent rate.

[Travis]

I never have like instrument approaches!  (I hardly go out if the sun isn't)  I usually just:

Find runway.

Land on runway.

Take off.

Repeat.

[Poseidon]

Well flying IFR with VFR approach and the last instruction I receive from the control is to maintain 3000 ft, turn towards the runway and then they give me clearance for visual approach, isn't this the intercept altitude? If I am not wrong this means after this point I have to start the final approach (always in case of no ILS). My point is that this sometimes happens in 3000 ft at 6 miles from the runway and other times 2200 ft at 7 miles. Obviously if I have to descent immediately I have to use a different descent rate in the two cases. Having ni ILS how can I decide when to start the final except pure visual? At what altitude/distance I should start the descent using the "Speed/2*10" formula mentioned berore?

[Fredgirardo]

Hi everybody,

    I have like the little formula mentionned above. I am exited to try it. But I still have the same question than Poseidon in his last answer:  Without any DME, when we start to descend of final approach?

[OTTOL]

Fredgirardo, in real life, once your "cleared for the visual", it's at the pilots discretion to SAFELY descend. If you were on an ILS, and then "break out", even if you can see the runway, I would continue to use the glideslope for guidance. If it's a localizer/VOR with DME or just an airport with a VOR/DME, you can start your descent using the 3:1 rule.  Altitude X 3= Descent point or Descent profile. If I'm at 8,000 feet (above field elevation), I want to begin my descent at appx. 24 miles.   At 2,200 feet  appx. 7 1/2 to 8 miles.

My point is that this sometimes happens in 3000 ft at 6 miles from the runway and other times 2200 ft at 7 miles. Obviously if I have to descent immediately I have to use a different descent rate in the two cases.

When you're "cleared for the visual", at this point, it becomes the pilot's responsibility to determine a SAFE descent point.   What I am saying though, and we do this in the "real deal", even when we are cleared for a visual approach, we still use approach guidance(glideslope, DME stepdowns, PAPI/VASI). At some airports, this is  MANDATORY,  and is stated as such on the plate. Laguardia, Teterboro and Orlando(ORL) are  approaches that come to mind. At all of these airports, you must maintain the approach, even in visual conditions. I don't know if your misunderstanding the clearance. "cleared for the visual" does NOT mean immediately begin a descent. Unless your in one of the MANDATORY situations previously mentioned.