Is the correct formula for calculating your landing speed (Vref):

Vso x square root (landing weight/gross weight)
i.e. Your gross reference speed times the square root of your landing weight divided by gross weight?

So if my Vso is 60, my landing weight is 2300lbs and my gross is 2550 lbs then my landing speed should be about 57kts right? And then put everything back into INDICATED airspeed, not calibrated.

I believe almost all a/c have their landing reference speed calculated as 1.3 x Vso.

I think you are referring to the calculation that's required for the CPL flight test.

Your calculation is correct, except that you have to convert the 1.3 Vso from indicated to calibrated first.

See http://www.tc.gc.ca/civilaviation/gener ... /ex2.htm#b

Aviatard wrote:I think you are referring to the calculation that's required for the CPL flight test.

Your calculation is correct, except that you have to convert the 1.3 Vso from indicated to calibrated first.

Then you have to convert your answer from CAS back to IAS so you know what to fly on approach.

I made myself a chart for the 172 from 1900 to 2300 lbs in 50 lb increments and calculated the Vref for each weight.

You're going to make a great airline pilot.

Dagwood wrote:

Aviatard wrote:I think you are referring to the calculation that's required for the CPL flight test.

Your calculation is correct, except that you have to convert the 1.3 Vso from indicated to calibrated first.

Then you have to convert your answer from CAS back to IAS so you know what to fly on approach.

I made myself a chart for the 172 from 1900 to 2300 lbs in 50 lb increments and calculated the Vref for each weight.

Oh crap! That's why my touchdown point is always a foot or two off!

The problem is most pilots do not actually fly the approach at 1.3 Vso. Instead the FTU's teach a much higher approach speed. For example flaps 30 Vso for the C152 is is 55 knots and 1.3 Vs is 60 knots. Judging from the long float with a level or nose low attitude I regularly see at my home airport folks are flying much higher approach speed. So mahtewc if you are actualy flying 1.3 Vso speeds good for you. However for low performance aircraft like the C 172 practically speaking the max weight value works pretty well for all but very low weight landings. However there is nothing wrong in striving for precise and accurate flying for every manoever and making the effort to fly the "right " number, not some FTU made up number or worse accepting what ever speed the airplane happens to give you, is IMO quite admirable. I would suggest however you only really need you only need at most three approach speeds. One for the lowest possible weight (1 person 1/4 tanks), one for mid weight and one for max weight. The difference in 50 lb increments is not big enough to make the calculation worthwhile.

BUT The calculation of appraoch speeds is good, however the abilty to actually flying the calculated number on a stable final approach is the only thing that in the end matters.

One for the lowest possible weight (1 person 1/4 tanks), one for mid weight and one for max weight.

This is what I do and mentally interpolate in between. Especially flying a 206 or Cherokee SIX where there can be over 1000 pounds difference between minimum weight (one person and one hour of fuel) to max gross.

If you find yourself flat and floating, you are approaching too fast. You should hear the stall horn at touchdown.

Big Pistons Forever wrote:The problem is most pilots do not actually fly the approach at 1.3 Vso. Instead the FTU's teach a much higher approach speed. For example flaps 30 Vso for the C152 is is 55 knots and 1.3 Vs is 60 knots. Judging from the long float with a level or nose low attitude I regularly see at my home airport folks are flying much higher approach speed. So mahtewc if you are actualy flying 1.3 Vso speeds good for you. However for low performance aircraft like the C 172 practically speaking the max weight value works pretty well for all but very low weight landings. However there is nothing wrong in striving for precise and accurate flying for every manoever and making the effort to fly the "right " number, not some FTU made up number or worse accepting what ever speed the airplane happens to give you, is IMO quite admirable. I would suggest however you only really need you only need at most three approach speeds. One for the lowest possible weight (1 person 1/4 tanks), one for mid weight and one for max weight. The difference in 50 lb increments is not big enough to make the calculation worthwhile.

BUT The calculation of appraoch speeds is good, however the abilty to actually flying the calculated number on a stable final approach is the only thing that in the end matters.

+1 but at the same time I would still like to see that chart! If you have it, use it!

Dagwood wrote:I made myself a chart for the 172 from 1900 to 2300 lbs in 50 lb increments and calculated the Vref for each weight.

Just to clarify, I only used that chart on the flights leading up to the CPL flight test...

It's been 1.3 Vso since then

hey right on thanks for posting this thread. i don't recall flight school emphasizing or even teaching Vref.

You shouldn't 'always' hear the stall horn or see the light on touch down and definitely not be stalling it right on. That is not something to strive for. An obvious example is a healthy x-wind component (something near that 20% figure) or a gusty situation which requires a margin above.. the answer is a slightly faster touchdown speed so as to be in charge of how it plays out.

"minimum controllable airspeed"

Also, it is not always ideal to land with with full flap; if your forwarded loaded it can be difficult to land in a suitable nose up attitude in some types.

Every 50 pounds, tip of the hat to you! Thats a cool thing to do, that'd help one become a better estimator when needed because you've labored on such things in detail. We work in a field where the real law is numerically coded physics.

LOL

are you guys serious?

Go fly tailwheel for a while.



Meet the new breed of Canadian pilots

C-HRIS wrote:I believe almost all a/c have their landing reference speed calculated as 1.3 x Vso.

It's 1.3 times Vso times square root of weight ratio. So if you're at gross weight you have a square root of 1 which simply makes it 1.3xVso.

Isn't 1.3 Vso for when you don't have an approach speed listed in the POH?

I've always just used the approach speed from the POH and corrected for weight...

Vref in a 172? Jesus, people.

It's not exactly a plane you need to fly by the numbers. I'd personally recommend you fly a safe speed you adjust for the given situation and then fly by the feel of the yoke in your hands and the ass cheeks in the chair. You'll fly it a lot better.

paydaymayday wrote: It's not exactly a plane you need to fly by the numbers.

Well, again I think the OP was asking about the calculation for the CPL flight test and this is for the short field landing. In that case you do need to fly it by the numbers. Seventy knots on final is going to make you float, even in a 172.

Dagwood wrote:

Aviatard wrote:I think you are referring to the calculation that's required for the CPL flight test.

Your calculation is correct, except that you have to convert the 1.3 Vso from indicated to calibrated first.

Then you have to convert your answer from CAS back to IAS so you know what to fly on approach.

I made myself a chart for the 172 from 1900 to 2300 lbs in 50 lb increments and calculated the Vref for each weight.

What does your "chart" say when your ASI quits working? I have had that happen.

AEROBAT wrote:

Dagwood wrote:

Aviatard wrote:I think you are referring to the calculation that's required for the CPL flight test.

Your calculation is correct, except that you have to convert the 1.3 Vso from indicated to calibrated first.

Then you have to convert your answer from CAS back to IAS so you know what to fly on approach.

I made myself a chart for the 172 from 1900 to 2300 lbs in 50 lb increments and calculated the Vref for each weight.

What does your "chart" say when your ASI quits working? I have had that happen.

Slow to the stall horn at 1500, trim, give a swipe of nose down and ride it in.