Why wouldnt my aircraft climb??

[green dinosaur]

To cut the long story short, a few days ago I was flying a SEP that would not climb, even with full power. I was flying directly into very strong winds at the time. (around 40 kts).

Can anyone explain?? I have loads of hours, but this has never happened before!! Then all of a sudden I was out of this turbulence and the ROC shot up to 700 fpm.

[AerocatS2A]

My guess is that you may have been in the downward portion of a wave. These are often created in the lee of a mountain range in strong winds.

P.S. what the heck is a SEP?

[JEP]

SEP is Single Engine Piston.

If the reason was downdraft (spelling ??) consider yourself lucky, that the downwind component did not exceed the ROC of the aircraft.

A little more info on temperature, type of aircraft, engine and airfield elevation would make it easier to make "qualified guesses"

[Bre901]

As AerocatS2A says you were probaly in the downward portion of a wave, but, as you are quoting " turbulence" I would rather think that you were in a rotor (i.e. lower lever part of the wave system), which makes you even luckier (not a place to be unknowingly)

Introduction to leevawes & rotors (http://213.157.12.12/mwp/Beschreibengl.htm)

to follow JEP's tracks, a bit more info about location vs mountain systems w/r to wind and cruising altitude would make it even easier to make "qualified guesses"

[Shaka Zulu]

In a light a/c the most probable reason is a wind change.
Because of what you've explained you must have encoutered a Headwind and suddenly encountered a changing wind, most probable to a Tailwind. This will seriously degrade your climb gradient. Same problem for Jet aircraft

[ETOPS773]

Has happened to myself,instructor seemed to think i flew through an inversion.Mighty scary stuff!

[bar shaker]

A change in wind direction, sudden and severe enough to stop you climbing, will also show a big drop in air speed. Surely its a lee wave. These can be 100+ miles from the ridge that causes them.

An inversion is a band of cold air below a layer of warm air. Can be turbulent but wont stop you climbing.

[Shaka Zulu]

Mate the guy flies a Single Engine Piston aircraft, sudden sort of any type windshear will cause the above noted effect of being unable to climb. You don't need a lee wave for that to happen.
2 air masses etc etc numerous examples of sudden changes in speed and direction

[green dinosaur]

I was flying a PA28 with a 360 lycombing engine. The airspeed did not change so I guess windshear can be ruled out.

I was actually flying away from the mountains (thankfully!!) and the wind was head on!

[Final 3 Greens]

green

- Were there any CB/TCu in the vicinity? (downdraught & turb)

[White Bear]

On occasion flying across the mid west in the summer, where from 4000ft the view across the prairie in any direction is such, you could easily be convinced the world is flat, I have encountered a similar phenomena in my 172. Flying straight and level, you find yourself descending, the only way to maintain altitude is to enter a climb, sometimes as much as 500ft pr min. In fact there have been times where my climb has been so steep my IAS has been as low as 65kts, and only just maintaining altitude. A few minutes later, no problem maintaining altitude, and airspeed back to normal. This can happen 2 or 3 times during a 2 hour flight. I put it down to flying through sinking cooler air. Any thoughts?
Regards,
W.B.

[Skylark4]

Instead of slowing up and trying to climb out of trouble, assuming you have height to spare, why don't you do as a glider pilot does and stick your nose down and get the hell out of the area of sinking air. Gliders fly slowly in rising air to gain height and speed through sinking air to minimise the time spent losing height.

Mike W

[2close]

On my FAA PPL QXC second leg, routing at 3000' South to North along the Florida east coast between Space Centre and St Augustine, on a very bright October day with Few fair weather Cu, I observed ahead of me a not apparently threatening but very dark cloud - one off, stratiform and not like anything else that day - about five miles wide and a couple of thousand feet high, from about 3000 - 5000'. There was no precipitation falling from it so I decided to go under it. I dropped to 2000' and levelled off but as I neared the cloud I started losing altitude through no input from myself. I was now under the cloud and noted that I was going down about 700fpm so increased power to try and maintain altitude - no chance, so full power went on and I again tried to maintain altitude, but I was still going down. As my very inexperienced brain cell tried to figure out what the **** was going on I again checked the instruments and saw that the RoD had reduced but I was now down to about 700' and very aware of the possibility of becoming Great White food (over the water with coast on left). I realised I could not do a 180 as that would keep me under the cloud which was obviously the cause of my predicament so I decided to try and make the beach. As I made my decision I came out of the other side of the cloud and immediately began to climb.

It was a really spooky experience, coming across freak weather like that and it really made me aware that you have to expect the unexpected.

Anybody got any ideas what this was?

[skydriller]

Ive never had the sinking feeling you are on about, but I have had the opposite!!

By which I mean I was straight in to Peterborough connington from about 2000ft one afternoon in the spring, and started my decent as normal, then after getting to about 1500ft nothing happened, ie decent profile, but the thing would not go down.....chopped power completely, more flap and the same thing!!!....or very slow decent rate starting, so more nose down & flap max... I remember abandoning the approach around 8-900ft with the runway only just ahead.

Once I had done a circuit there was no real problem?!:confused:

I was obviously caught in a very big thermal, and it was the wierdest of sensations......I can only imagine what it must be like the other way around.:eek:

Regards, SD..

[Kolibear]

Sneaky things, clouds, arn't they?

You can be underneath one, get caught in a downdraft and pushed towards the ground, or you can be under one and be blown upwards in a thermal.

I wouldn't trust them myself :O

[Teddy Robinson]

a gem picked up from a seasoned alpine flyer many many moons ago re flying/surviving severe mountain wave conditions.. (probably SOP for glider pilots)
Obviously this is subject to MSA/Terrain/ATC constraints.

"lower the nose through the downdraft portion of the wave to transit as quickly as possible, raise the nose to attain the attitude for max angle of climb in the updraft portion .. the lower groundspeed keeps you there for longer and you get more space between you and the terrain.. avoid the rotor cloud like the plague .. that can kill you"


Fly safe TR

[Shaggy Sheep Driver]

.......the RoD had reduced but I was now down to about 700' and very aware of the possibility of becoming Great White food (over the water with coast on left). I realised I could not do a 180 as that would keep me under the cloud which was obviously the cause of my predicament so I decided to try and make the beach. As I made my decision I came out of the other side of the cloud and immediately began to climb.

It was a really spooky experience, coming across freak weather like that and it really made me aware that you have to expect the unexpected.

Anybody got any ideas what this was?

Lenticular cloud. They are the visible evidence of wave (they dont' move relative to the ground), and it sounds like you entered the downgoing section of the wave but flew through to the upgoing section before you got pushed down into the ocean.

SSD

[yellowperil]

if anyone's interested in wave, I can recomend "Exploring the Monster" by Robert F Whelan, about the Sierra Wave Project in the early 1950's

see more here: http://www.greeleynet.com/~rfwhelan/monster.html

It tells of gliders using wave to soar to 44,000 feet - higher than many aircraft of that era; and also the story of how the lift was powerful enough to allow a P-38 to climb with both engines off...! It's absolutely fascinating!

nb. The world gliding altitude record is currently 49,000 feet (14,938m) set in the Sierra Nevada mountain range), however Steve Fossett and the Perlan project hope to break this

yp

[takeonme]

maybe you just forgot to apply back pressure????

[--o-o-0-o-o--]

Experienced rotor effect once flying East of Pennines with Westerly wind........ the only way i can describe it is, i got thrown down 500ft in what seemed to be about 2 seconds, and had a white knuckle ride for about five minutes. Scared me to death, but taught me to respect power of the weather.

[witchdoctor]

SSD

Not entirely sure lenticular clouds would be a likely occurence over Florida (highest point 350' or so?), but never having studied their local met I would be most interested to find out if they are indeed a possibility.

[flopter]

I suspect variations in the % of Humidity within the airspace you are flying thru.

I've been working on a rule of thumb for adding the % of humidity
to Barometric pressures in the area we take off from, combined with temp.

It's a neat way of checking out just how well your aircraft will "lift" and climb on a given day.

For example take the following scenarios..

Temp 27 Deg C
Barometric Press 1025
Humidity = 50 %

Aircraft will fly nicely..

However,

Temp 27
Barometric press 1030
Humidity = 98%

Aircraft has good lift and engine performance.

Temp 27 Deg C
Barometric press 998
Humidity = 98%

Aircraft has poor lift and engine performance.

etc etc

There is a definate correlation between Temp/Barometric Press AND very importantly HUMIDITY.

% of Humidity seems to be forgotten in most equations.

Higher humidy = poor lift
Lower humidity = best lift

I beleive factoring humidity into our normal flight performance charts where temp/Baro pressure and density heights are used, it may explain a lot of prangs that have been caused when aircraft are loaded to almost capacity and then get into trouble on the "wrong day" where humidity sneaks up and is not factored into lift performance.

just my two cents worth. :)

[2close]

but the thing would not go down

If only I had a pound for every time I've experienced that on hot days in Florida (even in October), usually on finals - I recall one instance when the a/c started going up!

BTW I'd have four or five pounds by now!

2close

[2close]

I suspect variations in the % of Humidity within the airspace you are flying thru.

Funnily enough Flopter, the RH in FL during October 1992 was quite high, 80% + on most days as I recall.

At the time I was quite fit and capable of running 5 miles in half an hour but the first day I went out for a run - only about 3 miles but at normal pace - I nearly died, so God knows how the poor old clapped out C-150 was supposed to manage. Probably something like me now.

One thing though, have you formulated a working equation based on your rule of thumb that would give a fair idea of what to expect in high RH conditions? It would appear on the face of it to be a useful tool.

Best Regards,

2close

[Flyin'Dutch']

SSD

Not entirely sure lenticular clouds would be a likely occurence over Florida (highest point 350' or so?), but never having studied their local met I would be most interested to find out if they are indeed a possibility.



When you have strong thermals and strong winds you can get thermal wave over entirely flat areas.

FD

[flopter]

Originally posted by 2close
One thing though, have you formulated a working equation based on your rule of thumb that would give a fair idea of what to expect in high RH conditions? It would appear on the face of it to be a useful tool.

Almost,

I have correlated all the relative data from over 300 hours of flights that I've carried out over the last 12 months. (i.e during all seasons)

The trick now is to compile it into a chart or formula that is quick and easy to read/use.

I've tried a few layout combinations in the way of intersecting line graphs, and also a few formula combinations and it's starting to come together.

When I've completed and tested a clean prototype, I'll post it somewhere here for further testing.

-flopter

[Kolibear]

I'm slightly surprised that no one has yet mentioned microbursts or windshear.

The first time I knowingly encountered 'liftless air' :O , I was in a C152 with a friend. We'd left Southend with full tanks and had been airborne for about an hour. We were returning along the north Kent coast, upwind of the Downs, which had a large bank of cloud building over them.

The cold air blowing down out of the cloud was pushing us towards the ground and it was only the application of full throttle that kept us at the same height.

Neither my friend nor I are particulary large persons, so the aircraft was well below MTOW.It is very easy to exceed MTOW in a C152, two ample adutls and full fuel is enough. Factor in a tired engine and in my scenario, the aircraft would have been descending.

[sharpshot]

Bar Shaker

Please expand upon your extensive knowledge of inversions.

I thought I knew why the Met. Office puts out Warnings when an Inversion is known to exist.

:confused: