Do you know what a 'slinky' is? I hope so cause' if you don't you won't get my drift. Imagine the slinky is the atmosphere. Attach little tags to the slinky that correspond to different pressure levels. So at the bottom of the slinky I attach a tag that says "29.92", and above that (since the pressure will be lower) I attach a tag that says "29.01, etc. Note that the pressure level of 29.01 will always be above 29.92 because pressure decreases with altitude.
After you have attached all your tags stretch the slinky. All of the pressure levels rise. This corresponds to a hot day when the atmosphere has expanded. The altitude at which you will find 29.92 changes from day to day depending upon temperature and pressure. With me so far?
Now there you are at 5000' flying along with 29.92 in the little window on the altimeter (the Kollsman window) and the temperature drops. This causes the slinky to contract, which causes the 29.92 level to drop lower. This has all happened while you are flying along fat, dumb, and happy as you chase the needle on the altimeter to make it say 5000'. You have no idea that the temperature has dropped, or that the pressure has changed. What has happened?
Well, the pressure level that you were using to measure off of--29.92--moved downwards because the atmosphere shrunk. You chased the needle to make it say 5000' and this put you closer to mother earth, right? But you think "I am still at 5000', why does that mountain look so high?"
As has been said, the altimeter measures or references off of whatever you put into the kollsman window. It tells you how high you are above that level. Keep in mind that the pressure levels move up and down and that you are measuring your distance above that level and I think you will have your answer.
In your example the pilot changed the level which s/he was referencing off of. That level is physically higher so, if I were standing at the top of a 1000' tower and were measuring with my hand-held altimeter and I was first measuring the distance between me and the 30.11 level and then changed the setting to measure between me and the 29.96 (higher) level the altimeter thinks the distance has shrunk, right? So it will measure lower.
Antonio
Altimeter Indication
Second Problem
Which condition would cause the altimeter to indicate a lower altitude than true altitude?
A Air temperature warmer than standard.
B Atmospheric pressure lower than standard.
C Air temperature lower than standard.
I chose "C" because the altimeter reads a higher altitude in dense air (cool air), so if the temperature was lowered, the air would be more dense and the altimeter would feel closer to the ground?
David
The answer is 'A'. The word "indicate" in the question is the one to watch out for. The altimeter is *indicating* you are lower than you actually are. Another way to say that is: your true altitude is higher than what is indicated on the altimeter.
You can remember all of this by the old mnemonic: "High to low, lookout below. Low to high, you're in the sky". When you go from a high to a low you need to 'lookout below' because you are closer to the ground than the altimeter says you are--that is-- the altimeter is *indicating * higher.
The question asks, "What would cause the altimeter to *indicate* lower..." which can be tricky. The altimeter will *indicate* you are lower than you actually are when the temperature or pressure has risen. "Low to high you're in the sky" means that when the temperature rises your altimeter will *indicate* that you are lower than you actually are.
Antonio
Checkride Skills
The Problem
I'm supposed to take my PPL checkride on Sunday and seem to have developed Soft-Field-Landing-Block. Even my instructor is becoming a little frustrated as I had no problems with these a month ago. I am flying a Warrior and seem to be flaring too early. I guess I'm nervous about a prop strike. Does anyone have any tips?
The Advice
Just pretend it's a normal landing...BUT...after touch down keep the nose wheel off the ground as long as possible by keeping the yoke in your lap during the whole roll out. That's it. (Add a bit of power if you haven't kept some on and remove the flaps right away this will help the elevators maintain authority..) Oh and just for looks you may want to add a very small touch of power just before the mains touch. The DE isn't looking for perfection, just that you know the procedures and get them in the ballpark.
Personally, I can never get the "add a touch of power" thing. I never seem to find the happy medium and usually make the plane begin a balloon or if it doesn't balloon it distracts me enough not to flare properly. I just do a normal landing and keep the nose wheel off the ground as long as possible without using the brakes.
Kobra
Ah, the pre-checkride block. Take an instructor with you and low approaches flying just inches above the surface. You'll learn what power setting will keep you flying....anything less than that will put you on the runway. Don't worry man, come the big day you'll surprise even yourself.
Rodney
One of many reasons for doing slow flight and MCA is get ready for landings in general and slow flight in particular. Trick is to land as low and as slow as possible with minimum descent rate. This may very well mean landing with power, depending on the airplane.
Watson
Given a choice, I would rather be sure that you are ready for the check ride rather than make you take the check ride just because you are scheduled for it. If soft field landings are suddenly a problem for you, then I would hope that you can get them worked out before Sunday.
Have you tried looking further down the runway?
C. J. Campbell
Get your instructor to take you to a grass strip. Works for my students. Although somewhat harder to find, a runway with slushy snow works even better.
PD
That doesn't really sound like a soft field landing problem but a regular landing problem.
Unknown
I do something a little bit different (at least I think it's different) when I teach soft field landings. I try to focus a bit more on the mental state than the physical motions. After discussing the purpose of the soft landing and the objectives, I tell my student that I really like them -- that's not just a PTS task we have to get through. Instead, it's the landing that really makes you into a pilot.
Think about a typical landing. Roundout, pull power back, hold nose up, =hoping= that you did it right and =waiting= for the airplane to land itself. Many of us, me included, have found ourselves more passengers to the whim of the airplane than as PIC telling it what to do. (Not a bad way to think of it.) And we can get away with that most of the time.
In a soft field landing, like with a significant x-wind, we =have to= fly the airplane to the ground and on the ground. When the "touch of power" results in a balloon or excessive airspeed, it's because we haven't yet learned how to use the throttle to control our touchdown.
Although doing soft field landings on a 12,000 paved runway hardly simulates the real thing; it does have its advantages. One of the demos I do for a student is to do a soft-field landing, keep rolling
at least 1000' down the runway and take off again, all without ever letting the nosewheel touch. Just to show the kind of control you can get when you develop feel for pitch and power. My student can eventually do this himself.-
Mark Kolber
Try carrying some power (not sure of the best setting in the Warrior) all the way in until the mains kiss the runway, and then remove the power. You basically fly the a/c onto the runway. Full flap about half way down final.
Gary Spicer
I agree with everyone else...but the prop strike question bothers me. If you are not concerned about a prop strike during a normal landing (which should be on the mains, with the nosewheel coming down last), why would you get a prop strike with propeller discharge air over the horizontal stabilizer
keeping the nosewheel well clear of the surface?
Bob Gardner
When I was a student, my problem with soft-field landings was in fact flaring too late! My normal landings used to have a squarer flare than they ought to, and while I could get away with this most of the time, for soft-fields, the extra power meant that I'd either balloon out of ground effect when I tried my late round-out, or that I'd not get the nose high enough before we'd touch. Starting the pull back much higher and trusting in the extra power and ground effect to hold the plane in the air produced a much more nose-high attitude and allowed the plane to settle very, very gently on to the ground as required. It made an amazing change, and once my CFI had identified this as the problem, my soft-field woes went away.
Mike Granby
I don't think it's been mentioned (though Mark implied it) but theoretically in a soft field landing you have an endlessly long runway. This means that you have the entire length of the runway to stabilize and set her down nose high on the backside of the power curve.
My advice: Take your time and use up the whole runway. Fly a few inches off of the ground and don't let it touch down. When it wants to settle, add a little power and increase backpressure. If it starts to rise, release backpressure (If releasing back-pressure means letting the yoke move forward...DON'T) and/or reduce power. Keep her flying 'til she doesn't want to fly anymore! Once down, hold the nose in the air 'til it comes down on its own.
Antonio
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