1470ft Grass Field in a 172N

[Canuck1988]

I have a friend who has access to a 1470ft grass strip, and wants to fly her 172N into it (with me in it ).

The Strip:

1470ft x 50ft prepared grass
No large obstacles
Sea Level

The plane:

172N w/180hp

Now, I know the POH says it can be done, but will it be done?

Also in terms of take-off, the POH says for a soft field, you want a rolling start. But for a short field you want a static start. BUT WHAT ABOUT A SHORT-SOFT FIELD?!?! (Mind blown)

We are planning on marking off a longer local grass field to 1470ft and practicing there to get an idea of how this will go. Any tips or suggestions?

[Shiny Side Up]

First, remember you also have to get out of the field.

Lots of other factors too though. density altitude, wind and weight.

[PilotDAR]

The conditions you describe are entirely within the capability of this aircraft, with no unusual efforts or techniques -IF THE SURFACE IS FIRM. Obtain accurate information about the firmness of the surface. If the term "soft" or "wet" is any part of the description, either do not attempt, or walk the runway yourself first. If the ground feels soft under your feet - do not attempt.

Uncut grass more than 8" deep should be avoided.

Determine how you will establish the wind direction when you arrive.

Basic good short landing technique, with very good speed and "crossing the fence" height precision will get you in. Full flaps are important, and brakes may be needed. Getting in will be more the challenge than getting out.

Avoid soft field takeoff technique if the ground is firm, it will extend your takeoff run. Use the specified takeoff flap setting. I'm not keen on running up against the brakes, I just smoothly open the throttle, and go - but following the POH procedure is the "best" answer.

Hold the nosewheel light at all times. You don't need to be dragging the plane into the sky at the slowest airspeed, but a limp elevator and banging nosewheel is really bad. If the ground is rough, all taxiing is best done with 15 flap (about the same as a fully down aileron). Doing this changes the downwash over the tail, and aids the nose up control in keeping the nosewheel light. If you errantly got airborne with 15 flap, rather than the specified 10, the world would not stop turning. 0, 10, and 20 flap is specified for takeoff in 182's, just for reference.

If the runway looks short when you open the throttle for takeoff, that's not a reason to drag the plane into the sky prematurely, allow it to accelerate normally to a safe takeoff speed before forcing it into the air, and leaving ground effect. Once airborne, allow the plane to accelerate, and do not hit any obstacles. you don't need to hang on the prop to clear them by hundreds of feet. In that case, when clearing obstacles is assured, speed is more your friend up to Vy, than additional altitude. After Vy, climb normally.

[photofly]

Also in terms of take-off, the POH says for a soft field, you want a rolling start. But for a short field you want a static start. BUT WHAT ABOUT A SHORT-SOFT FIELD?!?! (Mind blown)

We are planning on marking off a longer local grass field to 1470ft and practicing there to get an idea of how this will go. Any tips or suggestions?

A very good idea.

In which direction does the field slope, and by how much?

Short/soft: depends what you mean by short. If it's a 1470ft with a 4' boundary fence and then oodles of nothing, that's a different story to 1470' with a copse of trees on the other side of the fence. In the former situation, regular "soft field" technique that gets you into ground effect early and you have no issues clearing a low fence. A soft field with an obstructed departure needing a steep climb out ... that's a conflict of techniques.

Respectfully I disagree with PilotDAR when he says that getting in is more of a problem than getting out. I regularly (in summer, anyway) put a 172N into a 2300' grass field. The approaches are clear, and with only a slight headwind down and stopped 6-800' down the field isn't an issue. Departing can be more interesting, depending on the state of the grass. Remember book figures are for a hard surface with a suggested increase for short grass. Long grass, mud - you're a test pilot again. Even after your practice on a longer (and therefore different) field, pick a no-go point maybe 500' (600'? you choose!) from the end of the field and if you haven't broken ground by then, time to abort. Don't be lulled into a false sense of security by the initially-good acceleration on your takeoff run. The first 30knots of airspeed comes quickly, the next 10 takes a while, and now you've got the most drag from that long grass, the last 5-10knots can seem to take a really long time as the boundary fence gets closer and closer.

You have 20hp over the stock 160hp 172N, so that's going to help your departure. Are you going to be anywhere close to maximum gross weight when you leave?

[PilotDAR]

My home runway started out at 700 feet of grass, with excellent approaches. With my STOL kitted 150 it was close, and a hot summer day was scary. In a standard 172M, I had to be light to make it work. In the 182A, careful getting in, no problem getting out.

When I lengthened it to 1400 feet, everything got easier, thought the 182RG did not like landing in, hard to stop. No problem getting out, even with a load. Now it's 2100 feet, and all is good.

Photofly is right for a standard 172, but for my experience, 180HP is the break at which a 172 will really begin to get out well. But that power does not get you in any shorter. The 182A was similar, you had to work to get it into a short or obstacle runway, but no problem getting it out. I had the 180HP taildragger into my home runway the other day, and in the 2100 foot runway length, I had reached 500 AGL when I crossed the far end on takeoff - but that plane is amateur built, and has an awesome prop!

When I was taught off airport landings in the helicopter, I was taught to scope out a landing area as though I was scoping out a girl in a bar: Size, slope, softness, surface, surroundings, obstructions and wind.

[trey kule]

If the runway looks short when you open the throttle for takeoff, that's not a reason to drag the plane into the sky prematurely

Write this down in big bold letters and repeat it. It is the best advice you will get here.

Many years ago I used to teach very very shortfield techniques and this was by far the single biggest problem technique pilots have. Use the runway. All of it. If there are no obstacles, you have 1399 feet of usuable runway.

The other technique is confusing holding the nosewheel light with dangling it 8 inches off the ground. The latter attitude will lengthen your ground run a great deal.

Dont be in a big hurry to use fancy techniques if they are not needed.

[Rookie50]

Kudos Canuck for even asking the question and being thoughtful about the risk. Great to see, from this low timers perspective who tries to be the same. If everyone was so thoughtful we'd have fewer accidents.

[Canuck1988]

Also in terms of take-off, the POH says for a soft field, you want a rolling start. But for a short field you want a static start. BUT WHAT ABOUT A SHORT-SOFT FIELD?!?! (Mind blown)

We are planning on marking off a longer local grass field to 1470ft and practicing there to get an idea of how this will go. Any tips or suggestions?

A very good idea.

In which direction does the field slope, and by how much?

Short/soft: depends what you mean by short. If it's a 1470ft with a 4' boundary fence and then oodles of nothing, that's a different story to 1470' with a copse of trees on the other side of the fence. In the former situation, regular "soft field" technique that gets you into ground effect early and you have no issues clearing a low fence. A soft field with an obstructed departure needing a steep climb out ... that's a conflict of techniques.

Respectfully I disagree with PilotDAR when he says that getting in is more of a problem than getting out. I regularly (in summer, anyway) put a 172N into a 2300' grass field. The approaches are clear, and with only a slight headwind down and stopped 6-800' down the field isn't an issue. Departing can be more interesting, depending on the state of the grass. Remember book figures are for a hard surface with a suggested increase for short grass. Long grass, mud - you're a test pilot again. Even after your practice on a longer (and therefore different) field, pick a no-go point maybe 500' (600'? you choose!) from the end of the field and if you haven't broken ground by then, time to abort. Don't be lulled into a false sense of security by the initially-good acceleration on your takeoff run. The first 30knots of airspeed comes quickly, the next 10 takes a while, and now you've got the most drag from that long grass, the last 5-10knots can seem to take a really long time as the boundary fence gets closer and closer.

You have 20hp over the stock 160hp 172N, so that's going to help your departure. Are you going to be anywhere close to maximum gross weight when you leave?

Field is as flat as it gets, and is close to sea level as it gets fairly short, firm grass, all bonus'. In terms of obstacles, there is one end perfectly clear, the other, no fence, but a country road, and then tall trees off to one side of the departure/arrival path. Close enough that you would want to start a very slight early turn out for peace of mind, but they are offset from the runway.

Obviously the first time we try to get in and out of there we will make sure we have a little as little weight as possible. We'll probably mark off the at least the halfway point on the field so we can use the 50/70 rule of thumb for takeoff. (70% of your lift off speed at 50').

The shortest thing I've landed on is 2000', which was no problem. But cutting it down a quarter is a bit.

Now back to take-off: static vs rolling start? I would assume if I was most concerned with the shortness of the field and not the softness I would go with static.

Thanks all for the suggestions and insight.

[DanWEC]

Simple. Do you think you'll get stuck if you stop? If no, then do a power against brakes takeoff right at the bleeding edge. Since you're on turf give 10*/First notch or whatever it is in a 172. Keep the nosewheel only just slightly light as PilotDAR recommended. When the plane comes off with that slightly extra backpressure (Try for maybe 5 kt less than normal rotation) keep adjusting accordingly to maintain the obstacle clearance speed stated for your plane with one notch. With that thing it's probably fairly yoke back and nose high for the first hundred feet, but I've never flown one.
The full soft field you get taught at an FTU and in the POH is best suited to a frickin mucky bog. From what you described its a firm grass runway. Make sure it is, but really, unless you're carrying a herd of cattle in the back, a 180hp 172 will be probably 150-200' up by the end of that 1500' runway in this config. You have nothing to worry about. Landing will require only slightly more technique.

[trey kule]

Good grief.
Pilot Dar gave such good advice that I quoted it and said write it in big bold letters..

Then this

(

Try for maybe 5 kt less than normal rotation)

Use all the bloody runway.. The example given does not require any obstacle clearance.
This horsing a plane off when you have runway left is an incredably stupid thing to do, and one day it will catch you. If you have runway left and no obstacles let the plane accelarate as close to normal lift off speed as possible (short field) .if its really really soft that is another issue.

I think this comes about from pilot training pretending a 5000 foot runway is a short field, and thus not learning to use as much runway as you can.


My advice is dont fancy it up. Add a bit of power with the brakes on and then let it roll as you bring up the rest . Make sure its going where you want it to. If you have to go full static power and use the whole runway you are playing at the very edge. 1400 of nice short dry grass is not a particularily short Field for a 172 in most cases ( yeah yeah...lets hear all the exceptions)

More inexperienced pilots get themselves in trouble doing things that just are not necessary.

And as a last comment, that nice grass strip can go from being a piece of cake to a death trap with changes in aircraft weight, wind, temperature, wetness, longer grass...good idea to think a bit about these things each time you usevit.

[PilotDAR]

Canuck, Fly the 172 in with due care, and appropriate techniques, and look forward to a very pleasant and rewarding experience, you're gonna be just fine.

I agree that some POH's say to run up to full power against the brakes. My preference is to not do this, primarily because most brakes won't hold the plane anyway and if they will, the grass still won't I would rather the plane move when I expect it, not when I'm not. The propeller is pretty well completely stalled, and thus very inefficient anyway. My opinion is that this is a recommended technique more to reduce pilot distraction for more complex engines, where the pilot must actually "set" power. It's a 172, just point it the right way, keep it straight, and push the black knob all the way - then hold it there.

An element to consider is that with the big power set, you've got a lot of torque which the brakes are holding (hopefully!). When you release the brakes, it's going to want to yaw left, so it's one more thing you've got to be ready for. I'd rather open the throttle gradually, and have that torque come in less suddenly, while the rudder is becoming effective to give you control.

On tailwheel planes, power against the brakes is less desirable, though I still have seen it specified in the POH. In one very torquy turbine taildragger I flew, I followed the POH technique, and had the poor thing screaming against the brakes at 95% power. When I let off the brakes, it headed left despite all my right directional control application, and I was looking at oncoming runway lights. I missed than, but it was very unsettling. I don't do that anymore!

As for the climb away speeds, clear the obstacle (if any) with the speed you need to land safely ahead if it quits. Please consider what I presented here:

http://www.avcanada.ca/forums2/viewtopi ... city+curve

The operation you're describing does not require any unusual effort, just pay attention, and don't be sloppy. Good on you for asking, always do, if in doubt, but you're about to get the first stage of bush pilot smile on your face!

[pelmet]

Do yourself a favour and have no time pressure for getting in and out. Don't land in the morning when there is dew on the grass or anytime it is not dry. Try a day with a nice 15 knot breeze down the runway. Depart when temperatures are cooler and pressure altitude is lower.

Assume that you will screw up the first several approaches and be ready for a go around which happens if there is any significant floating in the flare.

[DanWEC]

Trey, you likely misinterpreted. I didn't say anything about hauling it off early and dragging into the air. I was agreeing with the very point you were reinforcing from PilotDar. Just a shade of backpressure keeping the nose light and the plane will start to come off just a little early. Was guestimaitng maybe 5 kt, maybe too much.

[whistlerboy02]

Yes it can be done
and Yes its a bad idea
It's a lot of risk for no reason, and since your posting in the FT forum I assume its a rental 172 and you early in your flying career.
By all means practice it at another longer strip like you suggest, but leave it at that.

[trey kule]

Perhaps I did misinterpret you. The internet can be bad that way.
My impression was based on your suggestion to try and get it flying below normal take off. A 172 is not a numbers plane. It will fly when its ready as a rule, and if there is runway remaining and no other issues, trying to unstick it earlier is not a wise idea.

Take a look at the twin otter acvident from Muncho lake on you tube. Runway remaing when he pulled it off.

Pelmet mentioned something valuable and that is the overshoot and learning to hold the nose down initially to avoid slipping into the backside of the curve, or getting out of it. That is counterintuitive as people want to immediately raise the nose.

Best bet is to practice and make sure you can do precision landings.

Btw... 1400 feet is not really a short field strip for a 172. And before someone trots out a POH, the point is becareful of applying techniques that are not necessary...like the man with a hammer who sees a world full of nails

[PilotDAR]

Yes its a bad idea
It's a lot of risk for no reason

If the pilot flies the aircraft within its performance numbers, and with due skill, it is not a bad idea to fly a plane into small runways. Every time you fly, there is risk. If you're flying with due care and attention, you accept the risk, and you're within the "permission" for the use of the aircraft, building skill and experience is good...

That said, Trey is right, a 172 is not really a [performance] numbers plane, they just fly when they're ready. Something would have to be unusual for me to be concerned about taking one in and out of 1400' - even a 150HP version. But that's me, each pilot should reach their own level of comfort. Asking here for some peer mentoring is just good judgement in my opinion....

[photofly]

A 172 is not a numbers plane.

Actually, what does he mean by that?

[PilotDAR]

Trey Kool wrote:
A 172 is not a numbers plane.

Actually, what does he mean by that?

It can't read.

[kevind]

Mel Bakersfeld: Joe, this is Mel. There's no more time. Stop all engines and get out. Repeat. Stop all engines.

Cockpit qualified young man: Mr. Patroni, she won't take much more.

Joe Patroni: Well anyway, she's gonna get it.

Mel Bakersfeld: Joe, the plows are moving. Shut down and hold on! Joe Patroni! Do you read me? Acknowledge!

Mel Bakersfeld: Joe! Shut down!

Cockpit qualified young man: Mr. Patroni? Don't you hear him? Shut down.

Joe Patroni: I can't hear a thing. There's too much noise. Hold on. We're GOIN FOR BROKE!

Cockpit qualified young man: [after the plane gets out of the ditch] The instruction book said that was impossible.

Joe Patroni:
That's one nice thing about the 707. It can do everything BUT read.

[PilotDAR]

That's one nice thing about the 707. It can do everything BUT read.

One of my favourite movies (you're dating yourself Kevin!)

I've had occasion, most recently last March, to fly a new type from the right side. I often find that over there, I can't read either - usually parallax is the factor. It has never interfered with feeling what the plane would like to have done, based upon my application of power and pitch....

[kevind]

I was too young to see Airport at the theatre. I did see the other Airport movies first run. Dean Martin was great in this movie.

[Posthumane]

Good thread with some great info. I think one of the best things I did during my flight training is went with an instructor and another passenger to a *relatively* short grass strip several times to really get a feel it. It's one thing practicing on a 3000 foot runway, but it feels different when the trees are rushing towards you and there is a great temptation to haul it off early. We regularly went to a 1900' strip nearby fully loaded or close to it with standard power M and N models, but I usually try to keep it to about 200 lb under gross when I do it in my 145 hp model. We also did a 1500' strip with just two of us. These trips were all at 3500'+ density altitude. Landing in that distance was never an issue as long as you are precise in your approach speed and touch down where you intend. If you are having trouble getting down in time or are getting a lot of float, go around. Before you take off, I would suggest you mark the halfway point with something prominent and follow Sparky Imeson's rule that if you don't have 70% takeoff speed at the halfway point then abort.

[Canuck1988]

Thanks again everyone for the input. I'll let you guys know how it goes.

[pelmet]

I have a friend who has access to a 1470ft grass strip, and wants to fly her 172N into it (with me in it ).

Thanks again everyone for the input. I'll let you guys know how it goes.

Thanks,

Keep us up to date on all the details. Baseball terminology will do just fine.

[photofly]

We should treat this kind of like an open flight plan; if you don't post back in a week we'll assume you crashed and send in the pony soldiers.