Jul 12th

Stability matters

By Paul Hamilton

Yesterday I hid some of the worst turbulence I have hit in a long time. It was unexpected. Overall light winds predicted.  I took off 7:30 AM for a morning flight with an intro student. Climbed to 10,000 in glass calm air. A few rain drops but not much. Headed north for about 15 miles and started my descent. By this time the student was controlling the aircraft and doing a great job of it.

 FlyinInGlassPreBump.jpg

 

My hands were off the bar. At about 8,000 feet, to my surprise, airspeed drops and we stall, wing rises. I grabbed the bar to pull in and level the wing than hit with a gust and the airspeed jumps  to 80. Wow. This lasted about 2000 feet in a descent until it got glass calm again. I headed back to the airport and was going to go south announcing over the radio my intentions and one of my previous students announced over the radio hit had just hit severe turbulence where I was going. Flew back to the airport, did a couple of touch and goes in nice calm air and landed.

TrikeSmileAfterBump.jpg 

What happened? I fly many days when the sky looks the same. However, this morning there were some fresh cumulus above the cloud layer in the distance. Looking in greater detail at the winds aloft I see there was a ---  Rapid temperature drop: unstable air possible ---- note on the winds aloft. It was 10 C from 6000 to 9000. That is 3.3 C per 1000 feet. This is highly unusual. 2 C per 1000 feet is the normal lapse rate. In my weather to fly video I say that 3 c is highly unstable and 4 c is thunderstorm/tornado unstable.

UnstableLapseRate.jpg 

Looking back after we landed I saw virga in that general area where the severe turbulence happened

Moral of the story is that stability matters and at these numbers above 3 C per 1000 feet it can affect you during the early morning.

Jul 7th

912s simple cooling enhancements

By Paul Hamilton

Thought this would be a helpful subject for all 912 owners.

At 6000 feet MSL, 95 degrees F max continuous my oil temperature is at 250 F using Aeroshell plus 4, and CHT at 250 with Dexcool 50/50. This is within limits but higher than I want.

I was told by a very reliable source who has a similar installation (you may identify yourself if you want but I know you want a low profile), that if I add AMSOIL Coolant Boost to my 50/50 Dexcool  system, I will get 10 to 10 degrees drop in coolant temperature.

I was also told that if I go to the AmsOil motorcycle 10/40 fully synthetic oil I will get a 10-20 degree drop in oil temperature and that the AmsOil is better overall when running only auto/MOGAS.

Any words of wisdom or experience with these two cooling enhancements?  I am pretty much going to do them since it makes sense.

Will running at these temperatures lower the life of the engine?

Jun 23rd

See SilverLight Aviation with Delta Jet II trike and AG1 gyroplane at Airventure 2014

By Abid Farooqui
Airventure 2014 starts July 28 and goes through August 3, 2014.
SilverLight Aviation will be flying both a Delta Jet II SLSA and an AG1 gyroplane to the airshow.
We are displaying in the Ultralight Area (Barn) booth: 909. Come and see why these aircraft are the best values in the business.

AV14GLYPHwbox.jpg
Jun 20th

Sign Petition for fair representation of trike pilots

By Rizwan Bukhari

 

www.change.org/petitions/faa-610-sos-save-our-sport-open-pilot-representation-in-lightsport-rule-making

 

I think this warrants a blog space. I read this petition and signed it because among many things, it asks for fair representation of pilots. This is your chance to do so as well. It is one thing to sit out and do nothing about an Issue or you can after reading the petition (if you agree with the message) support it. I think in all important decisions that impact our sport, all of us should have a fair representation.

 

Rizwan

Jun 14th

SilverLight Aviation's Delta Jet-II scheduled to be S-LSA by FAA

By Abid Farooqui

SilverLight Aviation's version of the Delta Jet-II trike will get its S-LSA US Light Sport Aircraft certificate in the coming few days.

CARRIAGE:
SilverLight uses the carriage skeleton body sub-assembly from Halley factory in Hungary who has been partnered with us for over 9 years but that is where the similarities end.
The trike carriage is QA'ed to our specs and assembled at Zephyrhills, FL near Tampa. The wiring and avionics are designed and installed here, along with the powerplant installation. The props offered are the Aero prop or the upgrade to Sterna prop. Props are mounted with a 4" spool spacer to give plenty of clearance between the prop blades and wheelpant fins.

Full instructor package with back foot throttle and back instructor foot brake pedal and wing control bars is available as an option. Foot pedals are adjustable for up to 3.5 inches.

Trike carriage is available with standard 4 x 8.50 round profile tires with 3-wheel hydraulic disc brakes as standard or optionally with Turf Glide Tundra tires with a different wheel and brake package also with 3-wheel hydraulic disc brakes. These can also fit 6 x 6.00 aircraft tires.

Fuel tank is TIG welded 5000 series Aluminum of 14.5 useable gallons with fuel pickups with coarse filter strainers in it. Backup electrical fuel pump is standard. Two bags can fit under front seat and are provided as standard. Additional bags to go on landing gear fairings are optional. Leaf spring Aluminum landing gear gives nice soft suspention yet strong enough to take the hits.

WING:
The wing is called CHEVAL 12 and is specially developed by SilverLight Aviation and purpose fitted to Delta Jet-II trike with electric trim system. You cannot get this wing from anywhere else except from us. It has a speed range from 42 mph to 115 mph with cruise speed between 55 mph to 95 mph hands off. These are close to  real calibrated speed numbers not just what you see on the airspeed indicator. You won't be going in one direction and have a headwind and then turn 180 degrees and have a headwind still or at best not a tailwind anywhere near what you should see indicating bad installation/position errors in pitot/static system. Stall is almost non-existent in un-accelerated flight. In accelerated (turning) flight stalls are mild and easily controlled with no huge tendency to suddenly drop a wing tip hard.

The main thing about the wing is its sweet handling. Whether you are flying in smooth morning conditions, catching a sunset flight or flying at noon in mild to moderate convection. The wing gives a feeling of confidence and its light controls even 2-up with full fuel give you easy corrections to upset from its track. The wing absorbs turbulence and allows the pilot time to respond to turbulence with ease, giving a feeling of confident control.

In gliding flight, one can turn the wing to a medium bank and it has no tendency to roll into the turn further nor come out of the turn. With power application, due to torque turn to thr right tends to indeed roll in a little as expected which is easily stopped with a very slight pressure. During even steeper turns (45to 60 degrees bank), there isn't a need to push the bar out beynd a few inches (exxagerated J-maneuver) or high side (oppose turning in) excessively. 

Wing uses winglets as well as micro vortex generators for expanding efficiency (converts a part of the induced drag into thrust), speed range and improving tracking at very high cruise speeds.
http://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-15-DFRC.html

http://www.nasa.gov/centers/langley/news/factsheets/Micro-VG.html 

It uses a cross span band of re-inforced PX mylar fabric to control washout at load and speed and also a re-inforced dacron and mylar trailing edge. The control frame is tall giving extra leverage to the pilot which means less control force. Leading edge is PX or mylar with extra re-inforcement at the root for clean leading edge at the root.

Whether you want a 2.5 second 60 degree bank to 60 degree bank or a 65 mph leisure flight at 2.5 gallons per hour or a 98 mph cross country flight eating those miles up quickly, Delta Jet-II with Cheval 12 wing delivers.

This wing will be available to existing Apollo 912 or 912ULS powered trikes for upgrade if the customers wish with full documentation and records to keep their S-LSA status. 

POWERPLANT:
The aircraft is powered by Rotax 912ULS 100 HP engine. An engine with a ton of reliable history behind it and a standard in light sport aircraft. We have so far avoided the complexity of Rotax 912iS which though fuel injected new version of 912ULS is still in development and not matured yet. Besides its heavier, relies on batteries and more expensive. Once 912iS matures and Rotax settles on its final design, we expect to offer 912iS engine as well. Right now the fuel savings gained from 912iS alone are not justifiable by its extra cost, extra weight and complexity. The gain in fuel efficiency in 912iS is balanced by its extra installation weight because you can carry that extra fuel with 912ULS.

GROSS WEIGHT:
Through load and flight testing the gross weight is selected to be 1125 pounds. Maximum empty weight with all options including BRS (Ballistic Recovery System whole aircraft parachute, pull a handle and a rocket fires a parachute that brings the whole aircraft down slowly and safely) is 583 pounds. This gives a minimum useful load 542 pounds which is almost the empty weight of the trike without BRS. So in effect the aircraft can carry its own weight.

PERFORMANCE: (at ISA sea level unless otherwise noted)
Speed Range: 42 - 115 mph, Cruise: 55 - 95 mph (at 3000 feet)
Glide Ratio: 10:1 @ 51 mph
Climb Rate : 1350 feet/min (one up), 1050 feet/min at gross weight
Ground Roll: 300 feet
Take-off to clear 50 foot obstacle (tarmac): 750 feet
Stall at gross weight: 42 mph
Stall at 825 pounds (one - up): 36 mph
Approach speed recommended: 60 - 65 mph

Jun 14th

Delta Jet-II S-LSA

By Abid Farooqui
Jun 2nd

Measuring take-off roll at standard conditions

By Abid Farooqui
International Standard Atmospheric conditions rarely ever exist for long in any part of the country, yet all the performance data for aviation and pilot operating handbooks is required to be given at ISA conditions.

One such measurement is take-off roll or distance it takes to break ground by the aircraft at or near gross weight.

I talked about the importance of airspeed calibration before and I stated that airspeed calibration chart is about the first thing to develop carefully because almost all the rest of the testing depends on it. If your calibration is off, pretty much everything else will be off as well. This distance measurement is no different and we will soon see why.

Generally it is assumed that it is safe to break ground at 1.2 times Vs0. Vso being the stall speed (calibrated). As it turned out, we have a handy dandy formula to get a pretty close stall speed number for any weight once we know it at one weight (within reason).  This formula is:

Vs2 = Vs1 √ W2/W1 

Where
Vs2 = stall speed at weight W2, to be determined
Vs1 = stall speed at weight W1, known or measured

So my calibrated stall speed at 786 pounds was measured to be 35 mph with a very mild stall break.
Using this formula at a gross weight of 1100 pounds we get
Vs2 = 35 √ 1100/786
Vs2 =  41.4 MPH

So 1.2 x Vso = 1.2 x 41.4 = 50 MPH
This would be considered my TOSS (Take-Off Safety Speed)

Regardless of if I am a good enough pilot to break ground at this speed or not, the fact is that I can safely break ground at this speed. In fact the aircraft can fly just above stall speed but this leeway is taken for average pilot technique and safety due to weather variances.

So now that we have the speed, I just need to measure how long does it take in distance (or time) to go from 0 mph to 50 mph)?

Of course this should be measured on the ground run in very calm no wind conditions if at all possible.

There are as expected a few different acceptable methods of doing that. One is a grid photographic camera method, stopwatch with lap function method and recording voice for markers.

Since most of us do not have specialized equipment but we do have runway lights that are generally 200 feet apart (acting as markers, and Large white balloons can fill the 100 foot marker gaps) and our handy dandy smart phones with voice recording functions and usually an intercom with audio-out, this is the method that seems most practical.

Markers are set every 100 feet. Recording device is turned on. Pilot and co-pilot are seated in the aircraft. Aircraft comes to first marker, holds brakes and goes to full power, keeping wings level and neutral so as to give lowest frontal area to the relative wind to decrease drag. Pilot releases brakes and aircraft accelerates forward. Co-pilot records short abrupt and clear "GO" in the voice recording device. Aircraft passes second market at 100 feet, "One" is recorded, aircraft passes 200 feet or second marker, "Two" is recorded and so on.
Now make a graph of TIME (x-axis) and DISTANCE (y-axis on right hand side) and VELOCITY (y-axis on left hand side). Since average velocity is simply
Vavg =  delta d / delta t

TO-Dist-1.JPG

If distance is measured in feet and time in seconds (from the recording), then this speed is in feet/sec, so we have to multiply by 1.467 to get it in MPH
Vavg (mph) = delta d / delta t (1.467).

Each marker set, can give us an average velocity for that set. For example between 0 to 100 feet (100 feet was our marker distance), there is an average velocity, 100 to 200 feet we have another average velocity and so on. Using this average velocity calculation per set, plot a velocity graph which usually comes out to be a smooth curve.

TO-Dist-2.JPG

Now locate the average velocity of 50 mph (1.2 x Vso) on this curve. BUT this value must be TAS (True Air Speed). So take the indicated stall speed (IAS), correct it to Calibrated Airspeed (CAS) which in my case is within 0.5 mph and then correct that on your E6B to the TAS needed.  

Now that you know the TAS of your ISA 1.2 x Vso you can use your chart constructed (Distance, Time, Velocity) ... enter it at velocity, move down to distance and that is your take-off distance.

But that is your take-off distance at that non-standard atmosphere which can be off quite a bit from standard conditions. What to do now?
One Word: "Denalt Computer" by FAA.
A better usable version of Koch chart and almost a must for test pilots.

http://www.aprindustries.com/index.php/Pre-In-flight-Time/Speed/Distance-Computers/76-DAP-204-T/S/D-Computer-with-Density-Altitude-Performance-DAP-204.html
May 23rd

Airspeed Calibration - Acceptable method

By Abid Farooqui
Although there are various acceptable methods for airspeed calibration chart development like boom with low flying aircraft, chase plane etc., now-a-days GPS methods are becoming extremely popular. I have been involved in certifying some airplanes in recent years and that of course entails developing and executing a full flight test program. 
After some initial flights to test for rigging, engine function and reliability, one of the very first test flights is done for airspeed calibration because almost all the rest of the performance testing depends on getting to know your airspeed .. more specifically your calibrated airspeed (CAS) which can vary from your indicated airspeed (IAS). This variation is due to instrument error as well as static port position error. Any time our static port opening senses static pressure from wind blowing past it at a "different speed than aircraft true airspeed" it sees a different pressure and all instruments relying on static port produce unreliable results. These include primarily airspeed indicators, altimeters, and vertical speed indicator. One can see why airspeed calibration to get within a reasonable range is so important for the rest of the performance testing.

ASTM standard require that calibration show that throughout the range the error is no greater than 5 knots or 5%, whichever is greater. So how does one check this. Its actually quite easy technically with todays GPS technology.

FAA has an Advisory Circular (AC 23-8C) for testing means for Part 23 certified aircraft. This AC should be consulted among some other well written articles and books on flight testing. This AC can be downloaded from:
http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2023-8C.pdf

One of the methods described in this AC for airspeed calibration is the 3 track GPS method as recommended to FAA by National Test Pilot School (NTPS). This is described in Appendix 9, sub-section 3.

The method requires 3 ground tracks at the same airspeed and altitude. They can be almost any ground track. It is however advised that they be between 60 to 120 degrees off from each other, example,  40, 160, 280.

So for instance, you want to calibrate your airspeed. You put your trusty old handheld GPS or any GPS on your trike. Make sure it shows ground track heading. Make sure it shows ground speed in the same units as your airspeed indicator (knots, MPH, etc.) and to get enough data points you want may want to select 7 to 10 airspeeds. I for example selected, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 knots for CHEVAL 12 wing, I would select something different for say CHEVAL 14 wing which is expected to be slower.

You make yourself a data card which looks something like this for each data point (indicated airspeed) you want or you may even want to fill in the indicated airspeed (data point) in the air to what you can hold as long as its a bit different than your other data points. Your track can be dynamically selected as well as long as track 1, 2 and 3 for a single data point are flown at the same indicated airspeed and similar altitude. For next airspeed they don't even have to be exactly the same tracks. This makes aviating really easy and calculations longer but it can give us better accuracy.

ASI-CAS-Data-Card.JPG

Note that this data point is for one speed of 45 knots indicated (or as seen on my air speed indicator). Pressure altitude is gotten by setting the Kollsman window to 29.92 inches of Mercury, ground trach heading from GPS is recorded and outside air temperature (OAT) is recorded. You can use a cheap temp sensor from Walgreens as long as it reads the temp right.

It is completely unimportant what GPS ground tracks you do. Being further apart reduces chances of error so just do 3 approximately 90 degree turns and let things stabilize for 10 seconds at the desired airspeed and altitude and record gps ground track, ground speed, pressure altitude, OAT. Turn and do it again at the same airspeed and same altitude, turn again and do it for the third track. If the altitude remains within 50 feet, you will be ok. However if the airspeed varies even a couple of miles, you will get a big error. That is why early morning or late evening when thermal activity is low and at higher altitude like 3000+, you will get a good data point.

Now simply repeat this at 50, 55, 60 and so on airspeed data points also. You will notice that OAT does not change much if you stay at the same altitude or within 300 - 500 feet. So usually no need to change that once you get it.

Now you need to get what is referred to as True Airspeed (TAS) from this raw data and then adjust that true airspeed to standard sea level conditions to get your Calibrated Airspeed (CAS). 

How do you get TAS from this raw data?
Well fortunately, there is something called Microsoft Excel Worksheets where we can plug in formulas etc. This 3 track in any direction gps method was first described by Doug Gray (Australia) but really is a special case of the 3 track method used and described by NACA in the 1920's. It was adopted by National Test Pilot School in Mojave, Ca where they developed some complex Excel worksheets because they are dealing with aircraft where Equivalent Airspeed (EAS) and other things have to be taken into account. Since most trikes are not cruising at above 100 knots compressibility errors etc., can be ignored and I simplified the worksheet so we can just plug our numbers in and get Calibrated airspeeds out as seen below from one of my initial test runs. ( 1 knot = 1.15 mph = 1.852 km/h)

TAS-CAS.JPG




One can then also do some more handy work in Excel and get it to draw a calibration chart with a calibration equation, like an example shown below for an airplane I worked on and this calibration chart can be put into a pilot operating handbook for use by pilots.

Calibration-Chart-AS.JPG

 
I will try and upload the simplified excel sheet so people can do this gps test in good calm conditions and take 5 to 10 data points and plug the results in to see how close their airspeed indicators are reading to reality. Errors here may also suggest  errors in altimeter reading, and also in VSI reading which may mean that takeoff distance to clear 50 foot obstacles may be off as well.

ASTM standard for trikes does not require manufacturer to give airspeeds in calibrated, but instead only in indicated airspeeds which makes sense because that is what the pilot sees but when doing testing calibrated and adjusted to sea level speeds are used for standard performance metrics to be gathered correctly. Many of our trikes have open static ports at the back and depending on the design, they may be off or not. 

Anyway, if anyone wants to do some fun gps flying and collect some data at a few speeds and wants to plug it in, feel free to contact me at abid@silverlightaviation.com to see where your airspeeds may fall.