Calculating Approach speed --additions

[Woy Wogers]

My answer to Woy Rogers question is that if the wind suddenly dropped then your airspeed would remain the same, your approach angle shallower and you would land further along the runway.

goldeneaglepilot, thanks - that is my understanding of the situation also, and of course the opposite if the headwind increases, i.e. an increased angle of approach and a reduction in groundspeed, possibly resulting in an undershoot without intervention.

This is the point at which inertia comes into play - a force must be applied (increased lift and / or thrust), to change the steady state airspeed and / or rate of descent to correct the approach, and force = inertial mass x acceleration.

WW

[Chuck Ellsworth]

Slighty higher altitude a few knots faster.

I can understand your being able to judge a slightly higher height above the runway, however I am puzzled at how you know the exact difference in airspeed that close to runway contact?

[Maoraigh1]

"Fly the aeroplane as per POH and do NOT add ANYTHING for gusts, wind, people in the back, plagues of frogs or anything else UNLESS the POH so advises!"
If approaching for an uphill landing, on a 600 altitude hill top strip, with wind gusting 28 knots at a nearby almost sea level airport, instruction for how to crash.
Inertia will tend to maintain speed of aircraft relative to the ground.
Windshear will lead to airspeed loss. Inertia will have to be overcome to accelerate the aircraft, relative to the ground, to avoid stalling.
The POHs I've read do not give specific instructions for difficult strips.
As regards excess airspeed, I agree.
This month, I tried the effect of coming low over the fence, but with 70 kts, on a flat 700m runway, in flat calm. Without using brakes, I used all but about 30 metres.
But approach and landing technique have to be adjusted for runway and for weather, as well as for aircraft

[IO540]

A slightly different angle on the question is that one can fly the approach at 500kt, etc.

What really matters is the speed one is doing during the flare.

[Mark1234]

Originally Posted by Woy Wodgers

This is the point at which inertia comes into play - a force must be applied (increased lift and / or thrust), to change the steady state airspeed and / or rate of descent to correct the approach, and force = inertial mass x acceleration.

Pseudo science I'm afraid. You're applying newton in completely the wrong manner. Goldeneaglepilot is mostly right - and right to all intents and purposes, fly the trend, ignore the deviations in the main. I note you don't say inertia isn't real, just dismiss it as .01 of a kt. Inertia is very very real. That's precisely WHY the ASI goes up and down in the gusts, and that's why if you fly into a big windshear you have airspeed changes.

As best as I can explain it, inertia is the property of an object - I may be using the wrong scientific term, but it's dimensionless.

1) Remove the earth, (ground) wind etc, and your plane is floating in interstellar space going nowhere (bear with me!)
2) Now add in a big lump of air blown at the plane at 60kts. What do you think will happen?

Bet you say the ASI jumps to 60kts, not that the airspeed stays at zero and the plane jumps backwards at 60kts! You intuitively know that it cannot instantly move.

The frame of reference thing gets complicated.. Groundspeed is as you correctly state, irrelevant, so is airspeed. Inertia is the tendancy of a body in motion to carry on in the same manner. What changed speed is the *air*; for the aircraft to keep the same airspeed it has to accelerate / decelerate - The motion of aircraft has to change. It will return to equilibrium with the new air mass because that is all that acts on it BUT that cannot be instantaneous because of inertia. The lighter the a/c the quicker it will change. Microlights minimal; 747's massive.

Generally a 10kt instantaneous change is a pretty unlikely scenario. Gusts are generally variations, so will go up and down. A proper, windshear is the main source of an instantaneous and sustained change in wind.

If woy's example was from 1000, or 10,000ft I'd agree, the transient would be minimal in comparison to the overall glide, however at low level the ground might well be reached before the transient effect is overcome.

Also goldeneaglepilot, talk to some of your glider buddies about what the ASI does when you fly into a thermal - very often it will surge by a few kts. Old friend inertia again..

I do however completely agree with A and C, Beagle, Bose, etc. **except in very special circumstances, but 1) I'd avoid going there, and 2) by the time you do such things, you *know* what you're doing.

One note however

Originally Posted by Maoraigh1

Inertia will tend to maintain speed of aircraft relative to the ground.

The effect is true, but inertia is not relative to the ground, just that the ground has a very very large amount of inertia, and doesn't tend to vary it's motion too much

[RansS9]

Does the POH advise?

Anybody able to quote theirs?

Just looked at mine and it doesn't.But then it doesn't give any advice on approach speeds either--I'll complain to Curtis the next time I see him (Actually ---no I wouldn't --how can you complain to the man that gave us the S1 !)

Suggested pionts of agreement;

--we fly light planes not heavy planes the same rules MAY not apply.
--we don't want to carry anymore energy than we need
--we would rather hit the fence at the far end at 20kts than spin/stall in at the near end. IDEALLY we don't want to hit ANYTHING.
--low level windshear and inertia effects are a reality and potentialy dangerous.
--there are many factors to be taken into account aside from approach speed in determining whether a landing is safe. It just happens that aprroach speed is the one under discussion at the moment

"Inertia will tend to maintain speed of aircraft relative to the ground.
Windshear will lead to airspeed loss. Inertia will have to be overcome to accelerate the aircraft, relative to the ground, to avoid stalling."
IMHO the above is the best description of why I've read!!

Just to irritate the moderators I've started another thread (Flight Testing)on why 1.3 was chosen. Early indications seem to suggest that this is to do with large jet requirements. Now some will come along and blow that thoery out the water by showing the Royal Flying Corps used it to calculate approach speeds!!

[mad_jock]

But approach and landing technique have to be adjusted for runway and for weather, as well as for aircraft

I disagree with that.

If you use the same techinque which gives you best performace for getting into short strip it will always work on longer runways. If the runway is way long you just move your touch down point futher up the runway if you are stopping.

Everyone knows at INV you can get a PA28/38 C150 down on the numbers and be stopped by the first touch down marker. But time and time again the lights go sailing passed Foxtrot. Pilots going for 23 with 15knts of xwind instead of having it on the nose down the short. You ask them why they do it and they say its airmanship to take the longest runway. Which is of course pish. The lack of PAPI's and the apparent shortness of it makes them struggle on with 23 with sometimes hurrenous rotar when the short would be a piece of piss. But they really don't like the ground rush going over water and the deer fence on short finals. So they preffer to take an outside demonstrated on the long runway

[hatzflyer]

Beagle, you are talking absolute rubbish.
point one). I have owned 80+ aircraft over the years. I have never seen a POH that has a section dealing with windshear/sink /severe turbulance on landing.
Point 2). I currently own 3 aircraft. Not one of them has a POH. So how can I comply with your post?
Last Saturday I experienced severe wind shear in my RV4.I had a passenger and it was witnessed from the ground.My Rv has a climb rate in excess of 3000ft per min.( as witnessed by many peole on here).
At full power, fine pitch we were decending below the level of the trees on the approach and only just cleared them.

Please don't try to tell me that I could have just sat there without increasing power and speed and I would have been OK. I have somewhere over 10,000 landings including 28 total engine failures under my belt and I don't believe you.
Aviation is NOT a one size fits all passtime. I have pulled too many people out of hedges over the last 30 odd years ( a very high proportion of whom have been instructors[ a few of them from a famous " farm strip conversion" specialists] ) and as we are loading them in the ambulance or driving in to casaulty it is always the same " I just don't know why that happened, according to the POH we had plenty of room"

Mad jock, how can you say that you disagree with the statement that says you have to vary technique for different aircraft? So would you approach a short strip in a Longeze the same as a Cessna 150 with 40 flap?

[mad_jock]

The only thing you can do is the wind sheer training that commercial pilots get in the sim.

1. Max power and pitch to the stick shaker/stall warner.
2. Don't change configuration.
3. Start swearing under your breath.

Thats still not garanteed to stop you crashing. On a loft exercise we got a wind sheer event and from 5000ft we just skimmed the ground by 100ft before getting it back into the air flying again where an engine promptly packed in. I was expecting some rather straight talking in the debrief but all we got told was that we were the first crew out of 15 not to have crashed and sorry about the engine failure but the exercise was meant to stop there followed by a reset to practise windshear events.

[rans6andrew]

I find that, sometimes, there is a need to approach somewhat faster than Vs, even getting on for Vne. The exact increase is dependant upon the bladder pressure at the time. It is amazing just how much speed you can dump by a bit of spirited side slipping as you come over the hedge.

Rans6..

[mad_jock]

Now that reason for a spirited approach speed is more than acceptable in my book. Also being bored with a ground speed of 40knots when your used to shooting approaches at 140 knots is also acceptable. Fitting in and helping out ATC while operating into commercial airports is also acceptable.

But that is for experenced current pilots. The altering of the approach speed with some bollocks theory based reason is not accpetable. And the inability to do it properly is the key. Which I am sure you can without any difficulty.

[Chuck Ellsworth]

including 28 total engine failures under my belt

That is quite a lot.

I also have been flying for quite a while and can not remember more than maybe five total failures.

What kind of aircraft did you fly that had so many total failures?

[madlandrover]

Listening to wind reports can often give you a fair clue as to what to expect. EG a few months ago (bringing a twin back from Switzerland) I had the choice of diverting to Cov with wind on the ATIS of (approx) 22025G40 160V230 (for those who don't know it, Cov is 23/05) or continuing on to my home base for a reported wind of 20020G40 (Home base R16 for night ops). On paper surely better to go for Coventry? I carried on for home. Why?

Local knowledge mainly - I knew from past experience that winds like that at Cov meant swirling gusts around a set of hangars on very short final, and on that night (2mb difference between Cov and BHX QNH...) I didn't fancy adding rotor to everything else. I was also happier going into an airfield I knew well and had reasonable experience instructing at in most conditions, day or night. The subsequent arrival wasn't especially pretty (flew a high downwind at 2000' agl, then put some drag down and kept the speed up until shortish final, then reduce to Vfe and a bit more flap, with windshear taking care of the excess speed!) but the aircraft was useable afterwards.

So, the clues: "fun" wind speeds coupled with any terrain or other ground features that could change the airflow on final. And, equally importantly, as IO540 says: the speed that matters is the arrival speed - the approach speed mustn't overstress the aircraft, but that's about it...

[mad_jock]

He proberly was one of the first rotrax pilots.

Some of the test pilots for the permit boys were clocking up 10-20 engine failures a year. One guy I saw had 4 in one day of testing. I did say to him one was unlucky, two was getting annoying, three is taking the piss and four someone isd trying to kill you. Must admit on the fifth attempt they manged to complete the sortie.

[hatzflyer]

I used to do test/ ferry flying for a dodgy maintenance out fit no longer in buisness ( thankfully). The worst one was a Cessna that the nosewheel came down and not the mains, and the bloody nose wheel wouldn't go back up.That and the Tommahawk that filled the cockpit with avgas when the tap sprung a leak.
I was young and foolish then, now.......

Just noticed that the same poster has now asked the same question under the flight testing banner.
He asked in relation to light aircraft, he's had loads of answers relating to 250 tonne jets and aircraft fitted with retracts,slats ,spoilers,flaps , known ice etc etc.....Is it mee....????

[S-Works]

I was young and foolish then, now.......

Now you are old and ugly.......

[BackPacker]

Is it mee....???

So what you're saying is that over there there's even more anoraks than here?

Mmm. I might just drag myself over there sometime...

[RansS9]

Hatzflyer-- In my defense it's not quite the same question. This thread "CalculatingApproach Speeds--additions" the other "Why 1.3Vs for the approach?". Interrelated agreed but subtly and importantly different.

TIM
"the same poster"

[hatzflyer]

Not so much of the old if you don't mind!

[Big Pistons Forever]

my 02 cents

The questions should not IMO be how much airspeed should be added for adverse conditions but rather what is different during these approaches as compared to benign conditions and how do I prepare for those differences. I tell my students not to add any extra airspeed because the POH recommended approach airspeeds in all teh common trainers, provides plenty of margin.

The thing I emhasize for approaches in adverse conditions is the absolute requirement to recognize when the aircraft flight path and/or airspeed is diverging from what is desired and to take immediate action to correct those divergences. That and the importance of not forcing a bad approach. While a pilot should always be ready for a overshoot he/she needs to be doubly conservative when dealing with adverse conditions.