RPM setting for landing J170: What do you use?

[Rocketing]

Hi,

 

I have trained on a J170.

 

I would like to find out what are the different RPM settings used by members when they come in to land. When you throttle back at base, what is your 'procedure' and what are your RPM settings?

 

I understand that many go to idle (around 1000 - 1200 after carby heat on) and in a short field landing we need to maintain 55kts with around 1500 RPM. Why not just approach a normal landing with 1500 RPM at 65 kts?

 

For this discussion, lets assume it is a normal approach with no surprises.

 

 

[Gnarly Gnu]

Yeah in a 170 I normally go heat off and then run around 1500 - 1800 RPM for most of final then to idle just a bit before the threshold in slight to moderate wind conditions. I suggest it depends upon the length of your final leg also how much flap you are using, if full when it is applied, pax or not etc. Do what works for you, I doubt there is a clear right vs wrong method here as long as you don't get too slow of course but others with more experience may disagree.

 

 

[facthunter]

Rocketing, I'm not trying to be picky as nearly everyone talks of approach speeds as a fixed for type thing. A lot depends on the weight the plane is. Ie if you have two fairly large people and nearly full tanks you could be something like 150 Kgs heavier than if one person and nearly empty. The other factor is gusts and turbulence where you might add a bit of speed or use a bit more power on the approach. This means you will have a smaller approach angle to have the same speed result.

 

Your approach speed should give you a margin above stall. The stall speed varies with weight. 55 can be too slow. Nev

 

 

[webbm]

It's an interesting topic. When I started to learn up in Queensland, I would go idle when parallel to the runway threshold, slow to 70 knots then 1st stage of flaps and start my base leg. 70 knots all the way to just above flare height. Second stage of flaps was optional, if too high on final (but within limits), they would go down. Got to about 3 hours solo using this method.

 

When I moved down to NSW, a bit different. Power and flap settings don't change until the runway threshold is 45 degrees behind you. 2000 RPM and first stage of flap. At 70kts (pretty much straight away), start base. When established base, second stage of flap. Maintain 70kts same as before. Stick for speed, throttle for rate of decent (same as before) , but aiming for 2000RPM.

 

Took a bit of getting used to going from one method to a different one. Both have merit, so I won't give an opinion on which is better ('cause I don't have one). I believe the second one helps keep the revs up for low outside temps, plus gives more flexibility with the option of higher and lower power settings. The first is simpler to remember in my opinion and I'm sure the awesome CFI at the club would have more reasons... :)

 

Cheers,

 

Matt.

 

(I've left out stuff such as carb heat etc)

 

 

[Guest Andys@coffs]

So my thoughts ( may be worth $0 so see what you think....)

 

When you are training you are taught a formulae that works and then when you complete the training you are set free to really start to learn.

 

One of the first things you learn after the formal training is that while the formulae that you were taught for landing works there are also an infinite number of variations that can also work and may be better than the fixed formulae for certain circumstances ( sort of a rehash of what Nev said!) . I suspect that within recreational flying where most people correctly have their head looking outside the plane that other than a regurgitate of the formulae learned during formal training or type endorsement etc that most pilots vary their speed and approach angle and amount of flap used based on the circumstances of the time and the location and the feeling in the plane itself.......

 

I couldnt tell you what the speed, or throttle settings were on the last 10 landings I did, nor do I think I might have oldtimers in the beginings because I cant remember.....in my humble opinion they were all good, and all different and my aircraft is still serviceable (other than a faulty leakdown on 1 cylinder but thats not landing related!!) so my suggestion is dont sweat it, learn the formulae(s) that are needed during training and the performance envelope the manufacturer demands so you can stay within them and you'll do fine!

 

Andy

 

 

[winsor68]

My 6 or so hours of early training in the J170 would have had my sphincter up around my neck choking me if I was doing 55 knots on final... But... it was a tired old 170 and I was new to Recreational Aircraft.

 

I would love to try a new J170.

 

 

[Gnarly Gnu]

Stick for speed, throttle for rate of decent

Oh, you don't do that do you?

 

.....

 

 

[Rocketing]

Hi All,

 

Thank you for the information shared here. I am only asking to get a variety of techniques as we are all on a constant flight of education.

 

No where did I state that I try and land at 55kts on a normal approach. The POH states that for a short landing. My current technique is to slow down before base and then maintain 70kts down to final where I maintain 65 kts.

 

Thank you all for the contributions. Much appreciated.

 

 

[motzartmerv]

Are you stirring the pot Rocket?..Where did you get 55 kts from?? Thats the short field appch speed, full flap, level attitude etc..

 

The RPM required to maintain the appch speed of 65 kts and the correct angle to the runway varies with wind strength/direction, weight etc.

 

Maybe setting a power setting and holding 5 deg's nose up worked in your dads Mirage's but not in a j170 on a gusty day...lol

 

 

[Rocketing]

Are you stirring the pot Rocket?..Where did you get 55 kts from?? Thats the short field appch speed, full flap, level attitude etc..

Hi Motz, yip. That is the Short Field Approach speed with 1500RPM. The focus over here is on the RPM not really the speed as I am just trying to find out what people are doing with the RPM levels.

 

 

[David Isaac]

Well if ALL you focus on is the RPM, there is the danger that a lack of speed may kill you regardless of your RPM.

 

If you want to land accurately you need to maintain a nominated minimum speed for the configuration and use the throttle to maintain the descent rate. Yes I do use that method and have done all my life, I only fly single engine less than 5700kgs, some times a lot less ... LOL

 

EDIT: I changed some words so it doesn't sound condescending ... it wasn't meant to be.

 

 

[webbm]

Oh, you don't do that do you? .....

he he. Virtually every landing I do, I still hear one of my I instructors' voice when he got up me for not doing so. :). But I wanted to make the point that I haven't been taught to stick to 2000RPM, even if high or low. :)

Cheers.

 

 

[facthunter]

If you are using power on approach the variability of it is ( controlling gusts and arresting a too high sink rate) a big asset. Otherwise you are just making your approach angle shallower and you lose the ability to glide to the field. A secondary effect is to reduce your ROD ( sink rate) I believe sink rates over say 600' per min are getting a bit excessive. A thruster or SB drifter with two up, can get over this with a power off approach.

 

Pilots at "largish" fields can get into the habit of coming in a bit fast to make things easier and have more control authority. You will end up floating a bit much if you do this, and it is not a good habit to get into as you will not do well at a short strip. Nev

 

 

[Gentreau]

.........I understand that many go to idle (around 1000 - 1200 after carby heat on) and in a short field landing we need to maintain 55kts with around 1500 RPM. Why not just approach a normal landing with 1500 RPM at 65 kts? .......

If you start your descent late enough you can. It's a compromise between approach angle and power.

 

You could come in at 65kts with full power and a very flat angle and no forward visibility if you wanted to.

 

Alternatively you could be at 1000ft AGL with les than 1NM to go and still descend at 65kts and hit the threshold.

 

What's important is that you understand the effects of the controls on approach and can vary them accordingly to suit the conditions.

 

Flying by the numbers is mostly for commercial and fast jet pilots.

 

 

[David Isaac]

In my humble opinion a lot of pilots (GA and RAA) and some with quite some experience fly the final too hot (too fast).

 

You only have to be 5 knots too fast in a C172 and you will use 300 to 400 metres extra in the flare and float ... real bad in a short strip scenario and if you are not good at making decisions quickly to go around, you may end up through a fence. I see too many C172 pilots too hot and trying to 'wheel barrow' them on, not a pretty picture and very destructive to the nose gear, not to mention the prop tips if it goes bad. I am sure many of you have seen them.

 

I have always had it drummed into me that for accuracy of landing the correct speed for the configuration is the key and being set up in the correct configuration and speed early in the final (base speed is also important in slippery aircraft). None more so than in a proper 'short field' approach.

 

Why is this so important you ask ... for the reasons Nev has stated. If you have a habit of flying hot, one day you may find yourself planning a trip to a property that has a short strip or worse still having to do a precautionary landing into a short paddock, road or what ever is under you and if you don't know how to fly a 'short field' approach (minimum speed, maximum flap, if equipped), your bad 'hot' habits may make the difference between survival or not or simply damage to the aircraft or not. Please don't dismiss this possibly as 'it wont happen to me'.

 

I know I harp on about this from time to time, so please forgive me, but I think the two most important circuit types to practice are glide approach (with and without flap) and short field approach. If we can get these two practiced in both calm and gusty conditions, we give ourselves the best odds in a range of emergencies.

 

 

[Gentreau]

.......I know I harp on about this from time to time, so please forgive me, but I think the too most important circuit types to practice are glide approach (with and without flap) and short field approach. If we can get these two practiced in both calm and gusty conditions, we give ourselves the best odds in a range of emergencies.

Couldn't agree more, and I'd add "learn how to sideslip and be comfortable doing it".

 

Great feeling descending at 1500fpm, at approach speed and under control !

 

 

[David Isaac]

...great feeling descending at 1500fpm, at approach speed and under control !

LOL ... especially in a Drifter, I just love whacking them over into a side slip high on late final, they come down like an elevator ... great feeling and lots of fun.

 

 

[Gentreau]

Have you tried doing it in a Land Africa / Savannah / CH701 (all the same) with a big flat fuselage side to slow you down, it's like flying into a wall (of air) !

 

 

[facthunter]

If you just stand them on their nose, power off and aim a little short of your normal aim point they come down fast anyhow. I think 65 knots is their terminal velocity. You have a double flare. I was taught that by someone I believe knew what he was about with the drifter. SB. Nev

 

 

[David Isaac]

Nev,

 

Yes the Drifters do ... all that drag helps.

 

Gentreau,

 

No, never flown one of those ilks, but STOL is a design type I like and I would imagine the Savannah types would be heaps of fun to fly from the videos I have seen.

 

 

[Gentreau]

Actually it's just clicked as you guys are talking in kts and I'm used to km/h and just did the conversion, 65kts is bl**dy fast innit ?

 

VS0 for the J170 seems to be 39kts / 72kmh (wikipedia) which means you're using an approach speed of 1.66 x VS0 !!

 

That seems crazily fast. We normally teach 1.4 x VS0 for manoeuvering in the circuit and 1.3 x VS0 for finals, that gives 55kts in the circuit and 50kts on finals.

 

Is there some special reason that you would be taught to fly such fast approaches ????

 

 

[David Isaac]

Actually it's just clicked as you guys are talking in kts and I'm used to km/h and just did the conversion, 65kts is bl**dy fast innit ?VS0 for the J170 seems to be 39kts / 72kmh (wikipedia) which means you're using an approach speed of 1.66 x VS0 !!

 

That seems crazily fast. We normally teach 1.4 x VS0 for manoeuvering in the circuit and 1.3 x VS0 for finals, that gives 55kts in the circuit and 50kts on finals.

 

Is there some special reason that you would be taught to fly such fast approaches ????

It is fast from the point of view of convention and this has always been my curiosity with the Jabirus.

I have been told there are 'control effect' issues with the Jabs at speeds around 1.3 x VSo, which I believe is problematic if true. Any good design training aircraft should have full control authority at 1.3 VSo because after all that is the convention for short field approach speeds.

 

I am also told that Jabirus are rarely flown down final with full flap; that also has me bluffed, perhaps that is a control issue as well ... I cannot say because I have never flown one and would love to one day, they are a nice tough looking little Australian aircraft.

 

 

[facthunter]

Yes . You bend them if you try to fly slower plus we are all well fed here and we get a lot of thermals Cos it's hot mate. Most of the Jabs are not nice if you get them slow as the earlier ones particularly don't have a lot of rudder and aileron authority at slow speed. 5o knots would be slow and 65 is more than you need at any weight in calm air. . One version has a lower wing loading than the rest and tends to float on landing. Jabs are clean and will do this especially if the idle setting is too high. You can have directional control problems on the ground and it s generally advisable to keep the weight off the nosewheel , so high speed touchdowns are not good..Nev

 

 

[Gentreau]

Thanks Nev, it get's hot here too and we get some smashing thermals in summer especially when the farmers have only planted every second field, you you get a patchwork of dark green and light brown fields !!

 

Even in summer and thermally, we would use VS0 x 1.4 on finals, that's standard teaching here, which helps when you have to land on a 300m strip.

 

That applies to the slippery ones too, like a CTSW and an ATEC Zephyr which we have at out field. they both land at 90kmh for a VS0 of 65kmh.

 

David, those statements certainly don't give me much confidence in that aircraft, especially if they are sold for training.

 

.

 

 

[facthunter]

Although your question was not to me, the jabiru is strong and although it does have some characteristics that require some care they are in my opinion a plane which if you fly it well, you will cope with most planes quite well. It should be flown more precisely than many with a fair bit of attention to airspeed and not over controlling to ensure it goes exactly where you want it too. Bulldozer drivers do not apply. Nev