Archive for August, 2011

Lesson 4: Flight Control Effects Part 2.

Monday, August 29th, 2011 | Permalink

The lesson started in serious risk of being cancelled, as is becoming a bit of a ridiculous tradition for me, within 5 minutes of setting off for the aero club the first drops of rain fell from the skies!!   There was hope though, if all else failed my instructors 4pm slot had become free so we could cancel and try again later…….I should be more sympathetic of the rain we were getting, at the same time I was hoping the skies would clear, New York was getting hit by a hurricane!

G-UFCB Cessna 172SP

G-UFCB : Cessna 172SP

G-UFCB was the plane for today, in a punt that the sky would clear I checked out the plane.   I’m getting more efficient at plane check outs (efficient = faster,  without any shortcuts 🙂 ).  Nice to see Charlie Bravo in better shape, when I did my externals lesson on it, it was in pretty beat up shape.   Now it was looking good to go and as luck would have it the sky was beginning to turn blue!

With the lesson all systems go, we jumped in the plane and did the start up checks.  The airport had a CP-140 Aurora almost ready, so with a few “….that’s fine” additions from my instructor we were done quickly with the checks.

CP-140 Aurora

CP-140 Aurora

And then….

First Radio Call

I’ve been reading car license plates in phonetic alphabet for the last three weeks, so I was hopeful my first taxi clearance call would be ok.    We did a quick practice…….it went great, except my instructor said “Umbrella?  U is Uniform….”    I didn’t know where that had come from, I still don’t, I said it totally fluently, I hadn’t stuttered or stumbled, just rattled off: “Golf Umbrella Foxtrot Charlie Bravo..”     That’s what practise is for I guess!

“Ok when you’re ready, press the radio button and get our clearance…”

“……..Tower, Golf Uniform Foxtrot Charlie Bravo, Information with Bravo, QNH 1010, request taxi.”

“Golf Charlie Bravo, information correct…….”

Smooth and no stumbling or ‘errr’ moments, job done!!  Now to beat that CP-140 Aurora to the run way (if it got going we’d be delayed as they’d have priority).

Taxing to Runway

At the risk of my instructor seeing this and screaming I speak lies, my taxing is getting better 😉    I’m still not predicting the inertia as well as I’d like and have moments of overcompensation, but this lessons taxing was a lot better than Lesson 2 (Taxi / Ground Checks).   I also find myself leaning towards the more responsive effects of the brakes to due ‘good’ turns.  Just getting to the runway is not my definition of being able to do it etc.    It’s coming along though.

The Plane Air Traffic Forgot.….

We got clearance to take off, but as we were checking the runway approach, we spotted a plane coming down for a landing.   My instructor felt we were still good to go, so we went……but we later heard on the radio that ATC had semi-forgotten they’d cleared them to land and cleared us to take off!   [Why it’s vital to check the approach, even if you have clearance!]

Climbing through the Cloud Gaps

The goal was to see the effects of differing power and flaps, which we were hoping to do up at around 4000ft.   My instructor set us up on a climb through the gaps in the clouds and then passed control to me to try and “keep this picture”.    That went smooth, but unfortunately there was no horizon up there, so it was controls back to the instructor for a sharp decent to 2000ft.

The descents my instructor does always gives me a glimpse of how many more hours I’m away from being good at this flying lark 🙂

Changes in power, holding the planes datum, keeping it in balance and re-trimming I’m all pretty happy with.   On to moving the flaps.

Flaps and Oscillation

I should have realised this, but on the day I’d either forgot or the effect is just not that obvious enough in simulation.   Using the flaps makes the plane oscillate in pitch.

It’s obvious if you stop and think first (At least if you go back to initial & further effects of the flight controls!):

  1. Lowering the flaps to 10 degrees, gives a lot of lift.
  2. Lift causes the plane to pitch up.
  3. Pitching up causes the airspeed to drop.
  4. Reduced airspeed causes a reduction in lift.
  5. A reduction in lift causes the plane to pitch down.
  6. Pitching down causes airspeed to increase.
  7. Airspeed increasing causes an increase in lift.
  8. An increase in lift causes the nose to pitch up!
  9. …..and repeat, until at some point the plane will find its new equilibrium.

So if you lower flaps you get:   Pitch Up, Pitch Down….   If you’re raising flaps you’ll get Pitch Down, Pitch Up.

In flight this seemed fine and we did some practises of moving the flaps (always within the flap movement [VFE] speed of course!) and trying to keep the datum horizon out of the window.   Seemed fine, so on to playing with the aircraft fuel mixture.

Fuel Mixture Control

A question I always wondered, answered!!    On a Cessna with its push/pull rod controls, if you pulled the mixture control ‘all the way out’, the fuel would be completely cut and the engine would die!!!     Yet to ‘lean’ the fuel to air ratio, you have to pull the mixture control out.    Pull it to far out though and you risk killing the engine………so I’d always pondered this control, how did you make sure you didn’t accidentally pull too hard or get bumped?

It turns out the control has a second function:  You can twist it!

Done this way you’re always a long, long way from cutting the fuel.

We leaned the fuel and went from 10 gallons per hour fuel flow to more like 7 gallons per hour (fuel costs money: We’re now getting the same power for 3 gallons per hour less fuel!!).

On future flights I’ll have to keep a note of how much fuel my leaning has saved them and ask for the saving back at the desk 🙂

Time to head home…

I flew the circuit turns, my instructor flew the base leg and final approach with me feeling the flight controls, in preparation for that somewhere in the future, first landing of my own.    Once back on the ground, it was time for some more of my ‘self rated’ average taxing.    After landing checks done, taxi to parking done, shut down the plane and it’s another 55 minutes of flying signed off in the log book .

42.58 hours left to log.

Sennheiser Vs David Clark: Sennheiser Wins.

Friday, August 26th, 2011 | Permalink

Sennheiser HME-110 Side view

Sennheiser HME-110 Side view

They say the pub quiz rule is:

If in doubt, go with your instincts!

In the end that’s what I did to end the dilemma. My brain refused to accept that it could be possible anyone on this planet makes a better headset, at any relative level, than Sennheiser do.  So I bought myself a set of the HME-110.

A few people online recommended getting the replacement gel ear pads, so rather than risk having to pay postage twice, I thought I’d get some of those as well.

Today was my first flight using them (after many cancelled lessons due to rain!).

Verdict: The HME-110 is Absolutely stunning!

Anyone who reads my original post about the dilemma, go with all my pro’s…….forget any worries I had, they’re all nonsense.

Sennheiser HME-110 Special Edition Top View

Sennheiser HME-110 Top View

The weight difference is huge!

The HME-110’s are blissfully lightweight, yet feel rock solid in construction. In terms of weight I totally forgot I had them on in my flight.

Noise Reduction is fantastic and they don’t crush you’re head to achieve it either. I found the standard ear pads to be good, but I’m glad I got the gel one’s. Fit those and it’s another level of comfort. Add the gel ear pads to your order and you’ll still pay less than a set of H10-13.4.

I’d recommend them because they weigh so little and their noise reduction is excellent…….but why I’d really recommend them is because their sound reproduction is superb, I mean truly clear.

They are never going to match a set of studio monitors, let’s be honest about that, they’re impedance matched for an aircraft system so you won’t get the same raw volume if you tried. But in terms of frequency response, I’d believe the figures on the box any day, I tried them using some separate kit and their top and bottom end frequency response is sooo very good.

My worries about Microphone Boom Arm Radius:

Forget them, you can’t notice the boom arm in flight at all. It’s really just an optical illusion to some extent, once you’ve got them on, they’re lightweight the mic has enough reach to be perfectly positioned and the rest of the arm is outside your field of vision.

If you’re worrying about that boom arm, believe me, forget your worry just buy a set and when it arrives trust me you’ll go “What was I worrying about! How good are these!!”

Is it safe to fly in a General Aviation aircraft?

Sunday, August 21st, 2011 | Permalink

The probability of being in a fatal airline accident is ridiculously small, so small in fact that if you make it to the airport, the odds are well in your favour you’ll get to your destination airport (The chances you won’t are around 0.5 x 10^-6)*.

Airliners have lots and lots (and lots!) of redundancy in their systems and propulsion though, so you’d expect that even if they suffer a single failure, they could ride it out and land safely somewhere……..General Aviation aircraft, particularly your typical Cessna style Single Engine Piston powered machine, have somewhat less layers of redundancy (the lack of a second engine being the obvious one!).

Next to pilot error, engine failure is going to be the most likely cause of an emergency / accident.   It’s about 0.00315789% probable of occurring* (2006-2007 it happened just 24 times for 760,000 hours flown by GA aircraft, 4 of which were on the ground).

As a result, the rules for how low you can fly come from Rule 5 of the ‘Rules of the Air’, it’s goal is to ensure pilots are flying high enough at all times such that should they suffer an engine failure, the pilot has enough altitude to make an emergency landing without endangering those on the ground.

It defines three key provisions:

  1. 500ft :  An aircraft must not fly closer than 500ft to any person, vessel, vehicle or structure.
  2. 1000ft: When flying over the congested area of any city, town or settlement, an aircraft must fly high enough to land clear of the area without damage to people and property on the surface should an engine fail.  OR fly not less than 1000ft above the highest fixed object within 600m of the aircraft – whichever is higher.
  3. 1000 People:  When flying over an organised open air assembly of more than 1000 people, the aircraft must fly high enough to land clear of the assembly without danger to people and property on the surface should the engine fail.  OR fly not less than 1000ft above the assembly – whichever is higher

So how safe is it to fly in a single engine piston class general aviation aircraft?   EASA (European Aviation Safety Agency), have done some risk assessment work.

They found that the fatal accident rate in a single engine general aviation aircraft caused by engine failure, was 0.66 x 10^-6 per flight hour (0.00000066).    So statistically, you’d have to fly a little over 1.5 million hours before the accident would occur……I’m willing to bet most non-instructor GA pilots in the UK don’t clock more than 100 hours per year, so statistically it’s still an unbelievably safe way to travel.

* EASA Risk Assessment Report

Red Arrows Pilot Killed

Saturday, August 20th, 2011 | Permalink

This story was just breaking as I left for my subsequently cancelled lesson.   We had it on the TV at the aero club while waiting for the rain to clear.

The amateur video footage made me think it was highly unlikely anyone could have got out – but one of the guys there seemed to know more suggesting he’d ejected, a ray of hope at the time.

Sadly it has now been confirmed that the pilot (Flt Lt Jon Egging) died in the crash.

I’m no expert, but from the footage I find it hard to believe it could have been anything but a mechanical failure of the plane.   The pilot is unquestionably one of the best in the business.

All thoughts are with him and his family.

Flight Controls: Initial and Further Effects

Saturday, August 20th, 2011 | Permalink

Lesson cancelled due to rain, it started 5 minutes before my lesson was due to start and ended about 10 minutes after we called it quits on waiting for it to stop!

In the checklist of “Firsts”, in the hope we’d have got all the ground work done and be ready to hit the skies the moment it cleared:  I got to do the checks of the plane on my own, in the rain……Smart instructor!  🙂  To be honest it was a warm day and it was nice to be at the airport and walking round the plane.

What we were ment to do today was the practical of Initial and Further Effects of the flight controls.

Any action made on a planes flight controls has an initial effect, followed by a further effect if you continue that action without adding any additional control action.

So for example:

If you fly straight and level and then turn the flight control yoke to the right, the airplane will begin to “roll” to the right.  What you’re actually doing is increasing the amount of lift on the left wing by lowering its aileron (a bit like the effect of lowering the flap) while simultaneously reducing the lift on the right wing by raising its aileron.   The net effect is that you alter the torque around the planes centre of gravity and the plane rolls right…….that’s the initial effect of the action on the ailerons.

The plane is now rolling, a side effect of which is that the plane now has less lift, as a result it’s slipping out of the air nose first (because it’s heaviest).  This slipping or turning around a centre point (centre of gravity) is Yaw.   The further effect of the action of the ailerons is Yaw.

Left uncorrected, the yaw will generate more roll (because the further effect of yaw is roll), the increased roll will generate more yaw, the increased yaw will generate even more roll and on and on it goes putting the plane into a spin!

Flight Control Initial Effect Further Effect
Ailerons Roll Yaw
Rudder Yaw Roll
Elevator Pitch Airspeed

Once you make an action that takes the plane out of balance, you need an additional action to bring it back into balance or you will suffer from the further effect.   Thus when rolling the plane, you need to apply rudder to stop it yawing.

…….and that is initial and further effects of the flight controls, now all I need is blue skies to go and try it out for real.

Headset Dilemma (Sennheiser Vs David Clark)

Wednesday, August 17th, 2011 | Permalink

Normally if you asked me about headsets, I’d tell you go directly to Sennheiser, when it comes to closed monitoring of sound, they’re the best.   Use a pair of HD-25’s and any definition you had of a good set of headphones for monitoring sound (particularly with VERY HIGH background noise) will be shattered.

If you look at commercial aviation (airliners), you can see much of the HD-25 in Sennheisers’ range of commercial aviation headsets (e.g. HMEC 26).

When it comes to General Aviation, I’ll admit to being a bit shocked.   At the General Aviation level, David Clark is pretty much the standard.

I’ve worn them, I’ve looked at their technical details  and generally done what I guess a lot of first time aviation headset buying people will go through:  Spending a lot of time trying to work out which way to go.

As you’d expect online lots of people have very polar views on who is best and why….but it’s vaguely fair to say the H10-13.4 or H10-60 are the Passive favourites of the David Clark camp.   For Sennheiser it’s the HME 110.

The HME 110 is the same as the 100, the difference is simply:  Black caps, softer pads and the head cushion has been made softer – so technically the same thing, but for the black caps alone I’m ignoring the HME 100’s.

David Clark:  The Pro’s.

  1. Largely the Industry Standard
  2. More compact design relative to the HME 110, with emphasis on the radius of the microphone arm is on & the size of the mic. wind screen
  3. A military product look of robustness.

…and to be honest, then I start to struggle.

Sennheiser: The Pro’s

  1. Arguably slightly better Noise Reduction Rating 24dB [David Clarks: 22-23dB]
  2. Much better headphone frequency response range (45 – 15,000Hz) [David Clarks typical response range of 200-5,500Hz]
  3. Better Microphone response range (200-5,500Hz) [David Clarks (H10-13.4) is 300Hz–3.5KHz]
  4. Lower Weight (350g), roughly 25% less than the David Clark models [DC’s 10-60: 623 grams / H10-13.4: 467 grams]
  5. Warranty…….I’ve heard a lot of people talk about spare parts for David Clarks, true.   Sennheiser’s response would appear to be:  “Spare parts?  You won’t be needing those, have a 10 year warranty on us”).

Human speech is 60-7,000Hz range, as such for best reproduction you want something that has a frequency response at least twice this range (Can you see where Sennheiser is going with it’s frequency responses yet).   Anything that can’t respond to this range will be dependant on picking up the harmonics of the original frequency…….so in theory if you put out a sound around 60Hz, the DC’s will only pickup the 4th harmonic of that sound.

That’s the theory anyway, I have v.good hearing – how good it is at top and low end frequencies while a Cessna’s engine is roaring in the background is another question.

Sennheiser size

I think the best video of the HME 110 in use I’ve seen is this, you can see what I mean about the radius of the mic boom arm, relative to other headsets.

The last bit is my only concern, but having watched a few other videos (and also the fact it’s not stopping the above video user operate  a massive camera), I’m starting to be less worried.

Other videos of Sennheiser & DC’s in use

HME 110, side view in use.

HME 110 & DC’s in use in the same plane

HME 400 or 460 and David Clarks in use in same plane

……next lesson is in a couple of days, so I’m gonna have to resolve this dilemma pretty soon and order one or the other!

Aircraft Ground Checklists, Taxing & Turns

Saturday, August 13th, 2011 | Permalink

G-UFCB Cessna 172SP

G-UFCB : Cessna 172SP

Lesson 2: Pre-flight aircraft checks, aircraft start-up checklists, taxing turns and shutdown.

85 – The number of checks, before the plane is started.

39 – The number of checks, after the plane has been started, but before you can take-off.

This was a ground only lesson, going through the following areas:

  • Where the club keeps the books
  • Aircraft keys and documents
  • External check list for the aeroplane
  • Internal (Pre-start, Pre-Taxi and Pre-Take-Off) checklists
  • Taxing
  • Turns & Tight Turns
  • Shutting down the aeroplane

It’s Exercise 5 of the PPL Course book.

As you can see from the shear numbers, there’s a lot to check.

G-UFCB as we found during the checks, was in a bit of a beaten up way.   Good news from my perspective:   Instead of talking about “if it has a bald patch on the tyre…”, this plane actually had one.   Instead of trying to imagine what a plane looks like when you can’t see any of its front gear Oleo this plane had no metal visible (even when the instructor pushed on the stabliser at the back to try and lift the nose). So from a lesson perspective, a good plane – at the end of the day the plane was already scheduled in for maintenance.

My first ever taxi was never going to fantastic, but for whatever reason no matter how hard I pushed on the left rudder pedal, the plane wanted to keep going right (I guess it knew its way to the runway!) – the instructor had a go and commented on it.   However, you can turn a plane like you can turn a tank – break one side and the difference in power will cause it to turn.

We did some turns, some tight turns (using the brakes), probably got in the way of a couple of people wondering “why are they spinning a Cessna round and around…” Then taxied back to the parking area, the taxi back was a bit better.

After Landing & Shutdown procedures (Just 17 checks), the lesson was done.

Before starting this course I’d done a lot of simulator stuff, read a lot etc.  What I realised today is that what you just can’t learn without doing it, short of having a like-for-like hardware simulator, is how it all feels:   How much friction is there on the throttle, what it actually feels like to set the heading indicator etc.   What does it feel like when the rev’s drop 100RPM.

Finally, the Cessna photo is not mine, so credit to John Allan

Air Traffic Service Units: Call Signs

Wednesday, August 10th, 2011 | Permalink

Think of air traffic services units and most people will think exclusively of “Air Traffic Control“.  However, not all airspace is “controlled”, but you can still have radio communications with an air traffic service and in many cases the communication will sound not dissimilar to what a typical person would assume to be ‘Air Traffic Control’ (e.g. Class F airspace)……..Call signs are what differentiates the type of service you’re talking to.

Air Traffic Control Unit (ATCU): “Control”, “Radar”, “Approach”, “Director”, “Tower”, “Ground”

Aerodrome Flight Information Service (AFIS): “Information”

Aerodrome Air/Ground Communication Service (AGCS): “Radio”

Without going into detail a Control Unit has the highest qualified employees and you’ll be dealing with professional controllers who’ve passed a set of CAA exams, an ATCU is the only service which can provide a Clearance (A Permission or Instruction to act).   ‘Information’ will have you talking to someone who’s passed a few less exams and likely have less equipment, as such they can only provide ‘information’.    Finally AGCS means you’re talking to someone who has a ‘certificate of competence’, AGCS can only give information with regard to the aerodrome itself and any traffic they know about.

If ATCU’s are the only people who can tell you to do something:

  • All other actions taken are the responsibility of the Pilot In Command (PIC)
  • It’s really important to know who you’re talking to!

Because Callsigns are the only means of telling who you’re talking to:

It is an offense to use an inappropriate Callsign.

As such, if an AGCS started declaring itself to be “Tower” or “Control” (instead of “Radio”).  They would be fast tracking themselves to having their licence removed and potentially other legal actions taken against them.

It’s worth a reminder here that there is a difference between the types of “Air Traffic Services” and the types of “Air Traffic Service Units” described above.

The Extra 200 that didn’t want to fly.

Sunday, August 7th, 2011 | Permalink

The Extra 200 that did not want to start its engine!First flying lesson done and with my externals lesson on the horizon, this weekend it was all lined up to be a “fun flight” in an Extra 200 – somewhere between clocking up a bit more time in the air and just having fun doing some aerobatics.

Upon arrival to the airport I’d watched the Extra 200 land, blue skies and good visibility – the gods were seemingly being kind to us today.

Pre-flight briefings done, flight suit on, headset plugged in and canopy closed we were ready to go…….

That is we were ready to go, in the 20 minutes since it had landed the Extra had decided it was less happy about going back up.   The “Oh…” from the instructor in the back seat was a give away sound of ‘Hmmm the engine hasn’t started and this is not looking promising.’

While my instructor assured me the battery was not flat, as far as the Extra was concerned it was flat – perhaps a stuck solenoid was the running theory.  My instructor made calls to various people and tried a few things to bring it back to life, but there’s a limit to what you can do before you start needing CAA aviation mechanic approvals and we were reaching that point quickly.

So sadly, it was so close but not to be (at least not today).

Re-booked and my instructor pointed out that the silver lining to this story is that in a few weeks I’ll have had more lessons under my belt, some if not all of them with him, so when I next get to try the Extra I should be in a better place and be trusted to do a bit more with it!

Buys Ballot Law

Friday, August 5th, 2011 | Permalink

In a previous post I talked about Buys Ballot Law (Finding Low Pressure)the danger of flying on a constant indicated altitude (caused by not updating the altimeters pressure setting).

Buys Ballot Law is a means by which you can work out if you’re flying into high or low pressure, from effects that will be felt on the airplane performance & direction.   Hopefully setting off the mental spark of “I’m not updating my altimeter!!”

In the Northern hemisphere, if you stand with your back to the wind, the low pressure is on your left.

This is because in the northern hemisphere air flows clockwise around high pressure areas and anti-clockwise around low pressure areas.  Thus no matter which area you’re in, if you have your back to the flow of air (wind), to the left will be low pressure.

In the southern hemisphere the inverse is true.

Practical Use

So if an aircraft is getting blown/drifting to the right (the wind is coming from the left of the aircraft).   If you were to turn your back to the wind, your left would be in the direction the plane was flying……thus the plane is flying into low pressure (and the altimeter, if not updated, will begin to over-read).

The reverse is also true, if the wind is coming from the right and pushing the plane left.  Then the plane is flying into High Pressure and the altimeter will begin to under read if not corrected.