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-   -   stall warning and when to panic (https://www.pprune.org/private-flying/530865-stall-warning-when-panic.html)

wishful av8r 30th Dec 2013 11:16

stall warning and when to panic
 
I often fly with a much more experienced pilot. Conducting night circuits for recency requirements, I was a little perplexed turning onto final from base with a little wind behind us that my more experienced friend was banking greater than 30 degrees while the stall warning alarm was going off at 500 feet, yet didn't do anything to correct i.e. increase speed or reduce bank angle. My friend does have a a slight hearing problem so I assumed he was not hearing the stall warning. We did a touch and go but on crosswind he said he was happy with the speed turning final. I have only 250 hrs and I have a spinning endorsement but my friend has over 2000hrs and I was a little freaked out that he wasn't concerned about the stall warning alarm going off at 500 feet. Am I just too pedantic? I would really like advice form those with more experience.

tecman 30th Dec 2013 11:24

When you say 'going off' do you mean blaring, or 'peeping' with gusts? Some aircraft (mine included) have the stall vane set pretty conservatively, and are also more prone to peeping than e.g. typical SE Cessnas. That said, I would be concerned about too-steep turns in the circuit at night.

Dave Wilson 30th Dec 2013 11:27

I'm only a 200 odd hour guy myself but if I heard the stall warner turning finals I think I would have been in 'I have control' mode, regardless of the experience of the handling pilot. It's your neck on the line as well.

teknow 30th Dec 2013 12:04

I learned in Tomahawks (good spinners) and the one thing I remember being drilled home more than anything was 15 degree angle of bank on turn to finals, no more than a single stage of flap and AIRSPEED! 70 knots, add 5 if you feel unsure/uncomfortable/weather conditions dictate it! I never forgot this ...

I am currently "refreshing" ], and the only thing to add to this (apart from the Cessna 152 is 65 knots and you can use 2 stages of flap as there are 3 on the Cessna's), is don't start the final turn below 800ft QFE.

I'm no expert, but these are all lessons I don't think will every leave me due to the fact they have been shouted at me so many times!!!! :O

mad_jock 30th Dec 2013 12:23

You were taught a load of rubbish then teknow. And the 800ft is a load of rubbish as well unless its some noise rubbish.

As for the stall warner going off and not doing anything its bad form especially at night. A chirp or two is acceptable but continuious is silly.

fireflybob 30th Dec 2013 12:38

The finer point that's often not fully learnt is that when you roll into a descending turn you need to adopt a slightly lower nose attitude to maintain the (correct) speed.

mad_jock, I concur with your comments!

teknow 30th Dec 2013 12:52

I'm a low hours PPL, so would appreciate an explanation to that!

I understand why the "taught" methods may be rubbished by a more experienced pilot - my understanding is these methods/guidelines are put in place to deter the student pilot being too "gung-ho" and doing something dangerous?!

Getting a little off-topic I guess but as an inexperienced pilot the moment I heard that stall warning, I'd be lowering the nose, reducing the angle of bank and applying power.

Local Variation 30th Dec 2013 12:55

Are you sure you have 250 hours?

OhNoCB 30th Dec 2013 13:04

Agree with points made above. A little chirp or two, especially if its a bit windy I would be okay with. If it was going off continuously I would be telling my friend (hopefully before the speed got THAT low) to check the speed and if he didn't remedy it I would take control.

teknow, I don't agree with those things that have been drilled into you, but I have never flown a Tomahawk. In general though, fly a proper speed, don't bank stupid amounts, and don't let the turn slip or skid. Those are the main things I would be concerned with. More than 15 degrees of bank I don't see a problem with (unless you're too slow and/or uncoordinated) and do it at a height that is appropriate to how tight you are doing your circuit. Flaps again I don't know for the Tomahawk but I see no reason to restrict their use on a 152.

Dave Wilson 30th Dec 2013 14:12

65kts for a 152? Bit fast I think. Tecnow it seems to me that you are flying at a 'add 5 kts for the wife and kids and then another 5 if there's an R in the month' type of place. Have a look at the POH (clues in the name...:)) for the correct speeds and techniques. Having said that if your club has a particular policy then you need to abide by it.

AdamFrisch 30th Dec 2013 14:20

When the load factors go up, so does the stall speed. Most have an understanding of this.

But did you know that in a 45 degree turn the stall speed goes up with over 40%? That's quite a lot. So, if you're low, heavy, have marginal speed already and gusty winds, it is imperative that you increase your speed either with throttle or by pushing nose down when you turn. There is nothing dangerous with a steep turn down low as long as you protect your speed. Or even better, install a cheap AOA meter and take the guesswork out of it.

A and C 30th Dec 2013 14:21

Teknow
 
I regret to say that you are the victim of poor instruction you flight should be arranged to arrive at the threshold at 1.3 Vs if I remember correctly the PA38 has a Vs (full flap) of 48 Kts so that should be 61.1 Kts.

65 Kts would be a reasonable speed to aim for on final with a reduction to 62 Kts ( I can't read the ASI to 0.1 of a KT) as you come over the hedge. If is was very gusty then 70kts is the maximum ( reducing to 64 Kts at the threshold) I would use in normal flying practice any more and you are going to float half way down the runway and risk all sorts of pilot induced oscillation problems near the ground.

mad_jock 30th Dec 2013 15:11

Its just part and parcel of the lack of attitude flying thats being taught.

They should add 2 circuits with all the instruments covered into the ppl test, that would sort alot of this pish out.


Reckon that 800ft is some nosense to do with commercial stabilised approach gate at 500ft. Its guff what ever the reason.


BTW the tommy is quite happy at 55knts approach speed full flap for a short field landing.

With 15 knts on the nose and 2 up and 2 hours in the tank you can stop in the space of the piano keys.

cumulusrider 30th Dec 2013 15:18

Adam Fritch said "But did you know that in a 45 degree turn the stall speed goes up with over 40%?"

Errr No! The stall speed will incease by a a factor of 1.19 at 45%. This would be logical as a glider with a stall speed of 40knts is often thermalled at 50 knts and 45 degrees. Source wikipedia

Dave Wilson 30th Dec 2013 15:34

Stall speed increase=square root of load factor. Therefore I put my money on Cumulus Rider.

Adam: At least you are erring on the right side of safety!

Flyingmac 30th Dec 2013 15:51



don't start the final turn below 800ft QFE.
Well with my base you'd be limited to a straight-in approach. (Circuit height 800'). At a neighbouring airfield the circuit height is 500' QFE. So, for you that would be another straight-in as you couldn't possibly turn final at 250'.
Could you?

Mad Jock is quite right regarding the Tommy and 55kts.:ok:

fireflybob 30th Dec 2013 15:53


There is nothing dangerous with a steep turn down low as long as you protect your speed.
AdamFrisch, nothing?

A and C, am with you but on a point of technicality our Flight Manual states 63 kts for scheduled performance etc.

For the record the load factor varies as the secant (ie 1/cosine) of the bank angle. Secant 45 degrees = 1.4 as near as dammit.

Stall speed increases by square root of the load factor - square root of 1.4 is circa 1.19 - there stall speed in 45 degree bank (level) turn increases by near enough 20%.

I knew there was a reason for all the trigonometry at school!

mad_jock, with you all the way about attitude flying etc.

Dave Wilson 30th Dec 2013 15:57

Firefly:

Unless I'm misreading what you are putting the load factor increases as the secant of the angle, not the stall speed. The stall speed is the square root of the load factor.

IE the load factor in a level 60 degree turn is 1/cos60 which is 2. So you are pulling 2g in a level 60 degree turn. The stall speed will increase by the square root of 2 which is 1.414. So if stall speed in level flight is 50kts, youre stall speed in a level 60 banked turn is 70kts.

Unusual Attitude 30th Dec 2013 15:58

The amount of chuff I've heard over the years from people who have no clue about the relationship between angle of bank and stall speed is astounding!

You can roll an aircraft to any flipping angle of bank you want without an increase in stalling speed as long as you don't load it up with G. People seem to lose sight of the fact that examples given to demonstrate the increase in stalling speed for a given angle of bank are only related to maintaining level flight in a turn.

For my own aircraft I know off the top of my head the 1, 2, 3 and 4g stalling speeds as these are of far more use no matter what amount of pitch or roll I have on.

Getting back to the original question, I was flying a G1000 C182 a fair bit until recently and the stall warner on that would go off so far above the actual stall that it was more of an annoyance than a benefit for a short field approach!

Regards

UA

Dave Wilson 30th Dec 2013 16:02


People seem to lose sight of the fact that examples given to demonstrate the increase in stalling speed for a given angle of bank are only related to maintaining level flight in a turn.
Er...thought that's what we were talking about...I agree with your other stuff by the way.

fireflybob 30th Dec 2013 16:09


Firefly:

Unless I'm misreading what you are putting the load factor increases as the secant of the angle, not the stall speed. The stall speed is the square root of the load factor.

IE the load factor in a level 60 degree turn is 1/cos60 which is 2. So you are pulling 2g in a level 60 degree turn. The stall speed will increase by the square root of 2 which is 1.414. So if stall speed in level flight is 50kts, youre stall speed in a level 60 banked turn is 70kts.
Dave Wilson, thanks for the correction - that is what I meant!

Flyingmac 30th Dec 2013 16:09

There are pilots who know the POH off by heart, and pilots who know their aircraft. They are rarely one and the same. It won't change.:rolleyes:

Dave Wilson 30th Dec 2013 16:17


There are pilots who know the POH off by heart, and pilots who know their aircraft. They are rarely one and the same. It won't change.
True but how many students are given the figures for approach and landing by their club and they turn out to be 5 or even more knots higher than the POH? (As tecnow has been given for his 152) First time they have a go at a short field after their license issue they're having a meet and greet with the upwind hedge. At least the POH gives you some info to work with, you can fine tune that to the aircraft you fly.

englishal 30th Dec 2013 16:19

Wot UA said.

Stall speed increases with wing loading, but if you don't load the wings - by not maintaining level flight - i.e. descending, then the load factor doesn't increase nor does stall speed. You could do a 60 degree bank to final as long as you are not trying to maintain altitude.

do a 60 degree wingover and you can have near enough zero IAS and no stall warner.

Dave Wilson 30th Dec 2013 16:22

:ugh: Don't think anyone is disputing that! :)

Unusual Attitude 30th Dec 2013 16:31

Perhaps not Dave but you'd be surprised the amount of pilots out their who really don't understand that concept and wet themselves as soon as you bank more than 30deg in the circuit.

UA

AdamFrisch 30th Dec 2013 16:32

Cumulus et al - you are correct. The 40% increase was for a higher bank angle, numbers were from memory and we all know how that is at old age.:8

teknow 30th Dec 2013 16:35

Just to clarify this (whilst not wanting to get into heated argument!) as I feel woefully under-qualified here ... :O


True but how many students are given the figures for approach and landing by their club and they turn out to be 5 or even more knots higher than the POH?
65kts on final turn. I'd then be looking for 60kts IAS on the final approach in the 152 with 2 stages of flap. If I need it, third stage keeping 60kts. Bearing in mind I have lots of tarmac in front of me, I'm happy with that.

The POH states 60-70kts (no flaps) and 55-65kts flaps down. With short field 54kts with 30 degrees flap selected.

For both types of landing, it goes on to say:

"Slightly higher approach speeds should be used under turbulent conditions"

I probably should have made it clear that 65kts was/is not my final approach speed.

I'm going to ask next Saturday about the 800ft thing ... I'm sure I've probably been told before, but can't recall the reasoning.

Dave Wilson 30th Dec 2013 16:37


Perhaps not Dave but you'd be surprised the amount of pilots out their who really don't understand that concept and wet themselves as soon as you bank more than 30deg in the circuit.
Due to lack of understanding of the principles of flight probably.

Dave Wilson 30th Dec 2013 16:41


I feel woefully under-qualified here ...
No you're not, I only have around 250 power hours, still wet behind the ears. I understand what you're getting at now with the 152, misunderstanding on my part. Not unusual...:)

S-Works 30th Dec 2013 16:48


I'm only a 200 odd hour guy myself but if I heard the stall warner turning finals I think I would have been in 'I have control' mode, regardless of the experience of the handling pilot. It's your neck on the line as well.
If you did that in my aircraft, I would tear your arm off and beat you to death with the bloody stump........

fireflybob 30th Dec 2013 16:54


I'm no expert, but these are all lessons I don't think will every leave me due to the fact they have been shouted at me so many times!!!!
teknow, good instructors shouldn't be shouting IMHO!

This thread proves what I often say about aviation - "Operating an aircraft safely is quite simple. It's just that there are a lot of people around trying to make it incredibly complicated".

The place and time to find out about lower speed characteristics of an aircraft is at a (safe) altitude.

Correct "normal" approach speeds are 30% above the stall speed!

There is a difference between the "signs of an approaching stall" and the "identification of a full stall". One sign of an approaching stall is the stall warner operating. Typically the stall warner operates at 5 to 10 kts above the stall speed.

As has been said previously there is a difference between the stall warner momentarily sounding or doing so continuously.

In a correctly flown circuit you shouldn't have to exceed thirty degrees of bank and I wouldn't want low hour students doing so. If you find yourself in that position better to level the wings (or reduce bank angle) and Go Around. Once settled back at circuit height do some analysis to trouble shoot how you got in that position to avoid same on next approach.

Piper.Classique 30th Dec 2013 17:03


Quote:
I'm only a 200 odd hour guy myself but if I heard the stall warner turning finals I think I would have been in 'I have control' mode, regardless of the experience of the handling pilot. It's your neck on the line as well.

If you did that in my aircraft, I would tear your arm off and beat you to death with the bloody stump........
Me too! Cheeky git. Mind, you would have a problem hearing a stall warner in a cub.....

Gertrude the Wombat 30th Dec 2013 17:08

Nonetheless, I warn my passengers under what circumstances it's normal to hear the stall warner, and if I were a passenger in something where it's normal for it to be sounding all the way round the final turn I would appreciate advance warning from the pilot!

Nearly There 30th Dec 2013 17:23


If you did that in my aircraft, I would tear your arm off and beat you to death with the bloody stump
Im assuming by that response you would be expecting a prompt first ie 'airspeed' If that failed and you still didnt respond to a stall warner I'd have no hesitation in taking control. argue about it on the ground alive.

Dave Wilson 30th Dec 2013 18:41


If you did that in my aircraft, I would tear your arm off and beat you to death with the bloody stump........
http://images.ibsrv.net/ibsrv/res/sr...er_offline.gif http://images.ibsrv.net/ibsrv/res/sr...ons/report.gif http://images.ibsrv.net/ibsrv/res/sr...eply_small.gif
You would have to be quick as the 'I have control' would probably be accompanied by an elbow in the chops. If I think I'm in danger the normal protocols of polite society are out of the window...:)

S-Works 30th Dec 2013 18:53

And where in your vast experience as a pilot have you developedthe ability to jump in and take control or have learned the necessary skills to make the decision that you are in danger?

Those of us who have been teaching and examining for thousands of hours still have to make margin calls on that one.

Your action of an elbow in the chops while illegally taking command of an aircraft are likely to get you and the commander killed......

Whopity 30th Dec 2013 19:37


You would have to be quick as the 'I have control' would probably be accompanied by an elbow in the chops.
From the UK ANO:

141 Every person in an aircraft must obey all lawful commands which the commander of
that aircraft may give for the purpose of securing the safety of the aircraft and of
persons or property carried in the aircraft, or the safety, efficiency or regularity of air
navigation.

142 A person must not while in an aircraft:
(a) use any threatening, abusive or insulting words towards a member of the crew
of the aircraft;
(b) behave in a threatening, abusive, insulting or disorderly manner towards a
member of the crew of the aircraft; or
(c) intentionally interfere with the performance by a member of the crew of the
aircraft of the crew member's duties.
Unauthorised take-over is a breach of Article 142.

Nearly There 30th Dec 2013 19:49

So the answer is let a deaf pilot spin you into the ground? I think an airspeed call (shout) would have been appropriate in this instance. x amount of hours shouldnt come into it.

The stall warner is there for a reason, if its constantly blurring during a turn you are approaching or at the stall. If the guy flying cant hear it and there is no visual indicator article 142 wont get you out the **** that is potentially developing.

piperboy84 30th Dec 2013 19:51

Tek now

The POH states 60-70kts (no flaps) and 55-65kts flaps down. With short field 54kts with 30 degrees flap selected.
Low hour duffer here also, but remember the POH is for gross weight which probably does not make much odds in a 152 with 2 folks in it, but flying it alone with 1/4 tanks probably leaves you 250-300lbs under gross which if I was flying I would knock 1mph off the approach speeds for every 80lbs I am undermax weight, not sure if this is the correct procedure but it does seem to get me in slower and pulled up quicker.

[SIZE=My advice is worth exactly what you pay for it[/SIZE]


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