Monday, May 28, 2007

Using an RMI

Those of us who did instrument training before GPS took over, had to learn how to do NDB navigation. An ADF is a very simple instrument. It simply points at the NDB. Follow the needle, and sooner or later you will get to the NDB – or possibly a thunderstorm. But such a seemingly simple instrument has been the source of a great deal of frustration to generations of pilots who had to learn how to use it for navigation. If our instrument instructors were successful in beating it into our heads, we eventually learned how to intercept specific bearings and track towards or away from the NDB in a more or less precise manner. The degree of precision often depended on the degree of wind.

VORs have radials, and NDBs technically have bearings. But to simplify this discussion, I am going to use radials in talking about NDBs. If we wanted to track inbound on the 180° radial towards the station, we learned to turn to an intercept heading, usually 30, 45, or 60° for ease of use. When the head of the ADF needle fell to the intercept angle, we were on the desired radial. If our airplane was really fancy, it had an ADF card that could be rotated. This simplified things for the pilot – more or less. If you remembered and had the time to do so, you could rotate the ADF card to match the aircraft’s heading. By doing this, you didn’t have to calculate intercept angles. When the head of the ADF needle fell to the desired radial, you had made the interception. Suppose you were southwest of the NDB and wanted to intercept the 180° radial and track inbound on it. You could turn to an intercept heading of 045° and also rotate the ADF card to match your heading. The head of the ADF needle would fall, and when it reached the desired reading of 360° (reciprocal of 180°), voila – you were on the desired course.

The ADF with a rotating card was often called the poor man’s RMI. It simplified NDB navigation, but having to constantly rotate the card really added to the pilot’s workload. But what if the card rotated automatically, just like your DG (heading indicator) or HSI. That essentially is what an RMI is. It is a DG with either one or two needles that can be set to respond to either NDBs or VORs. So using an RMI is basically just remembering how you did NDB navigation.

The RMI combines the DG and ADF into one instrument. As you turn, the card moves just as the DG or heading indicator would move.

Recently I was asked about using an RMI for hold entries. So let’s investigate how you use an RMI to get into a hold. To do this, set the RMI to respond to a VOR rather than an ADF. Assume you are tracking north on the 180° radial towards the VOR.

I have marked off the face of the RMI with the lines to determine holding entry for a right-hand hold. If you don’t recall this, please refer to Creating Holding Clearances. Our holding clearance at Podunk VOR was given as:

Hold northeast of PODUNK VOR on the 050° radial, right-hand turns, EFC……

This calls for a teardrop entry. To make this entry, we would turn to a heading of about 020° after passing over the VOR and fly for one minute (if it was timed legs).

Turning right to intercept the inbound course on the 050° radial, the RMI tells us right away that we need to stop the turn momentarily to intercept the radial.

Remember the RMI acts just like an ADF. The head of the needle is going to fall. Right now the plane is on the 40° radial, but we need to intercept the 050° radial. Since the head of the needle will fall, we can stop the turn temporarily on a heading of 200° and wait for the needle to fall. When it gets to 230°, we are on the 050° radial.

Modern RMIs include those that can track two different stations simultaneously and can be independently set to either VOR or ADF. This one is from a King Air panel.

It takes a little bit of readjustment to your thinking, but once you get the hang of it, it’s really a great instrument.

Sunday, May 20, 2007

Mnemonics and Acroynms

Mnemonics and acronyms – those little cryptic collections of letters and words that help us remember things. As pilots we certainly collect more than our share of them, and we all have our favorites that we tend to use, and teach. Some of my favorites include the following. They are not listed in any order or preference – just as I happen to think of them.

GUMP, BGUMP, BCGUMP, or BCCGUMP -- all variations of the same thing. Generally used as a pre-landing checklist, the letters stand for the following:

  • B – electric boost pump.
  • C – carb heat
  • C – cowl flaps
  • G – gas on the fullest (or correct) tank
  • U – undercarriage (gear)
  • M – mixture
  • P – prop

Red-Blue-Green -- this is the checklist I use on short final.

  • Red – mixtures should be forward
  • Blue – props should be forward
  • Green – gear had better be down

IMSAFE -- used for a pilot checklist. Are you safe to fly this particular day?

  • I – illness. You don’t need to be flying if you are sick. Go home and find your couch!
  • M – medication. Are you taking any medications, prescription or OTC, that would make you unsafe? Cold medications often make you sleepy, and a sleepy pilot is definitely not a safe pilot.
  • S – stress. Are you under stress or an emotionally draining situation? If so, you don’t belong in an airplane.
  • A – alcohol. No explanation needed. Alcohol and planes (and cars) don’t mix well.
  • F – fatigue. Are you tired and worn out? If so, you definitely do not belong in a plane.
  • E – eating. Have you eaten anything lately? A candy bar and a cup of coffee do not constitute a decent meal.

I once had a student pilot cancel her solo long cross-country. She got all the way out to the run up area and then taxied back in. When she called me to tell me she had cancelled, she cited the IMSAFE checklist. She was going through a messy divorce and decided she was definitely not safe. Needless to say, I commended her highly on her decision.

ABCD -- used for emergency procedures in case of engine failure in a single-engine plane at altitude.

  • A – airspeed. Trim for best glide. In a lot of trainer aircraft, this may be close to full nose-up trim.
  • B – best place to land. Pick out a landing spot and head for it. If you get there and you are high, you can spiral down.
  • C – checklist. If time permits, turn to the emergency section of the checklist to try to restart the engine. Otherwise use a flow method of checking critical items. Primer, boost pump, switch fuel tanks, carb heat or alternate air, mags (try one or the other).
  • D – dialogue. If you are talking to a controller, let them know you have a problem. Otherwise go to 121.5 and tell anyone within reception range that you have a problem. And if time permits, squawk 7700 on your transponder. But above all, fly the airplane.

Pitch-Full-Clean-Blue-Identify-Verify-Feather -- pre-takeoff checklist for multi-engine pilots. Treat every takeoff in a twin as “this is the day I am going to lose an engine on takeoff or climb out”. Review your emergency procedures before every takeoff. This particular set is for actions to be taken in the event of an engine failure on climb out after the gear has been retracted.

  • Pitch – pitch for the horizon, because your airspeed is going to bleed off at an alarming rate. Pitching for the horizon will preserve that vital airspeed and put you roughly in the vicinity of blue line (Vyse).
  • Full – make sure everything is full forward, mixtures, props, throttles.
  • Clean – verify you are clean, both gear and flaps retracted
  • Blue – put your airspeed right on blue line (Vyse), the airspeed for best single-engine climb performance. But just remember, there is nothing that says a light twin has to climb on a single-engine. However Vyse will at least minimize your rate of descent.
  • Identify – identify which engine has failed. Most multi-engine pilots are taught the “dead foot dead engine” technique. If you set your heading bug to runway heading and then use rudder to maintain the extended centerline, your “dead” foot will indicate the dead engine. Another clue is to use the turn coordinator – step on the high wing. The plane wants to yaw towards the dead engine, so stepping on the high wing identifies which engine has failed.
  • Verify – verify that you have correctly identified the dead engine by retarding the throttle for that engine. You don’t want to shut down your only remaining good engine!
  • Feather – close to the ground and fighting for altitude, that windmilling prop needs to be feathered. A windmilling prop creates an enormous loss of mechanical energy due to it forcing the crankshaft to rotate, which it turn causes pistons to move, etc. So get rid of that energy drain by feathering the prop.

Then climb to gain some altitude and come back for a landing. This in itself presents a dilemma. Climbing straight ahead is best for gaining altitude, but at the same time it is taking you farther and farther away from the runway. What is the best choice? Your decision. You can safely turn, even into the dead engine, but make it a very gentle bank and watch that airspeed.

PARE -- spin recovery. Although you may have not gone through spin training, you can’t get a Private Pilot license without at least having learned the situations that can lead to an unintended spin and how to recover from it, should it happen.

  • P – power to idle
  • A – ailerons neutral
  • R – rudder opposite
  • E – elevator forward

In most training aircraft it also works to just take hands and feet off the controls, and the plane will generally recover by itself. But you should remember the steps in case it doesn’t. If the situation presents itself, I strongly encourage you to take spin training. No amount of talking about entry and recovery can prepare you for the shock that occurs on your first up close and personal encounter with a spin.

ANDS -- this is another one all primary students learn about the behavior of the mag compass.

  • AN – acceleration will show a turn towards the north
  • DS – deceleration will show a turn towards the south

The 5 T’s – Turn, Time, Twist, Throttle, Talk -- Taught to generations of instrument students, it details the actions to take at various points in an approach or entry into holding. Not all of the T’s will be needed at every point, but running through the list will save you from an embarrassing omission.

  • Turn – turn to the desired heading. You may need to turn to an intercept heading to get on the desired radial or bearing.
  • Time – start your timer, if needed.
  • Twist – twist the OBS to the proper setting, either required radial or the reciprocal to eliminate reverse sensing.
  • Throttle – reduce your airspeed
  • Talk – if asked to report, do so.

TITS -- the mammary gland check, used to set a navigation radio and not forget something critical while doing so.

  • T – tune in the correct frequency
  • I – identify the VOR or NDB. That Morse code is there for a reason, so use it to make sure you have tuned in a properly working VOR or NDB.
  • T – twist the OBS to the correct setting
  • S – select the correct source, GPS or land-based VOR. Since the advent of GPS, the most common installation relies on a single VOR head to display either GPS information or VOR information. Make sure you know what is driving the VOR display.

One of the most common mistakes I see, as an instrument instructor, is failure to select the proper source. Some GPS units will switch from GPS to VLOC if the active frequency is a localizer, but don’t depend on the box to do it for you. You are PIC in the airplane, not the GPS, so make sure the signals driving the VOR display are coming from the desired source.

Stuff Out -- Vs and Vso, how to remember which is which.

  • Vso – “stuff out”, meaning gear and flaps, so Vso is stall speed in the landing configuration.

TOMATOFLAMS -- aid to remembering day VFR required instrumentation and equipment.

  • T – tachometer
  • O – oil pressure
  • M – mag compass
  • A – airspeed indicator
  • T – temperature gauge for each liquid cooled engine
  • O – oil temperature for each air cooled engine
  • F – fuel gauge for each fuel tank
  • L – landing gear position indicator
  • A – altimeter
  • M – manifold pressure gauge
  • S – seat belts

FLAPS -- aid to remembering night VFR required instrumentation and equipment, in addition to TOMATOFLAMS.

  • Fuses – spare set of fuses. Planes now mostly have circuit breakers.
  • L – landing light if operated for hire
  • A – anti-collision light
  • P – position lights
  • S – source of electrical power

“There is no more red port wine left” -- how to remember the position lights.

  • For those of you who are not sailors (which includes me), it’s one way of remembering that the red position light is on the left wing.

WRITMIM -- aid to set-up for an instrument approach

  • W – weather, ATIS or AWOS
  • R – radios set-up, both com and nav, active and stand-by
  • I – instruments, check both altimeter setting and DG
  • T – figure out time from FAF to MAP
  • M – missed approach point, make sure you know how it is to be identified
  • I – inbound heading, from FAF to MAP
  • M – minimum altitude, DH or MDA

“BLT with mayo, fries and a coke” -- created and used by one of my primary students, it was his method of doing a pre-takeoff check or a pre-landing check. He would also use it as a post-landing check. He was learning to fly in a Cherokee.

  • B – boost pump on or off
  • L – landing light on or off
  • T – transponder on ALT or stand-by
  • Mayo – mixture, either rich or leaned
  • Fries – flaps, either extended or retracted
  • Coke – carb heat, either on or off

These are some of the countless acronyms that are used by pilots. Do you have some favorites that aren’t listed here? Feel free to share them. It would both a lot of fun and informative to keep expanding this list.

Sunday, May 13, 2007

Procedure Turns

What really is the purpose of a procedure turn? It’s pretty simple – you’re going the wrong way and need to get turned around. We all learned about them – those little arrows on an approach plate, showing the direction to fly away from the course, generally for one minute followed by a 180° turn back to intercept the course going in the right direction. The one shown below is the Jeppesen method of charting a procedure turn

Instrument students were taught to fly it exactly that way. To deviate was to invite the dreaded pink slip from a disapproving examiner. However things are now starting to swing to a less strict interpretation.

But there are a couple of different types of procedure turns that must be flown exactly as depicted. One of these is the teardrop reversal, as shown below.

This procedure turn is from the ILS-18 at Lincoln, NE. To do this procedure turn, the pilot must fly out on the 324° radial of the Lincoln VOR and then turn right and intercept the inbound localizer course of 174°. Funny thing, it looks exactly like a teardrop entry into a holding pattern. The 324° radial is exactly 30° offset from the outbound localizer course.

The teardrop procedure turn must be completed within the limit specified on the profile view. The default value for this is 10 nm from the specified point or fix, but it can vary. The one for ILS-18/LNK is 12 nm, as shown below.

Another procedure turn that must be flown exactly as depicted is the holding pattern, as shown below for the ILS for Red Wing, MN.

If you have any doubt about whether the holding pattern is actually the procedure turn, check the profile view. That will clearly indicate that it is a holding pattern. In this case it is based on time, the tradition one minute. More and more however, the holding pattern is based on a DME leg length.

The purpose of both the teardrop procedure turn and the holding pattern in lieu of a procedure turn is to allow the pilot to lose a lot of altitude within a constrained amount of airspace.

As mentioned above, unless the procedure turn is one that must be flown exactly as depicted, then the pilot is given a fair amount of latitude as how to accomplish the procedure turn. The AIM actually states that the manner in which the standard procedure turn is accomplished is left to the pilot. This includes the point at which to start the turn, as well as type and rate of turn. Some of the methods include the 45° procedure turn, the racetrack pattern, the teardrop procedure turn, and the 80°-260° procedure turn. The only restriction is that it must be done within the limits specified on the profile view and it must be done on the protected side of the course.

One situation in which the charted 45° procedure turn makes a lot of sense is when doing an NDB approach (without a GPS). Then the charted procedure turn provides a 45° intercept to the final approach course. And when you are doing this type approach with only an ancient ADF providing guidance, that makes intercepting the final approach course a lot easier.

Years ago a retired Navy pilot showed me the 90°-270° procedure turn, and it has become my method of choice. As he explained it to me, this method is utilized by the Navy for man overboard, because it pretty much brings you back to the point at which you start the turn. The method is simple, and it involves no timing. Simply turn 90° in the direction of the protected side of the course and immediately start a 270° turn back in the opposite direction. This is a graphic of the 90°-270° procedure turn done in the sim. I did a screen capture of the track and made it into this graphic.

It’s easy, it’s efficient, and you don’t have to time anything. In actual practice, I teach instrument students how to do it both ways. This is a precaution against having an examiner who insists that it must be done in the traditional manner.

This brings us to the interesting question of when do you have to do a procedure turn. The AIM is pretty clear on this. You don’t have to do a procedure turn if you are being vectored, or if you are on a published portion of the approach that states NoPT. But with more and more GPS approaches being published, this brings up the question of why do a procedure turn when common sense clearly says one is not needed. Take the following example, the GPS-28 into Maple Lake (KMGG). It is clearly not the newer TAA style of GPS approach, yet it has something of the same shape and format – three IAF fixes, with one of the them being in the center.

Maple Lake lies west of the Minneapolis metro area, and is often used for practice instrument approaches. Clearly if you are coming from the east and are cleared directly to NAZMY, doing a procedure turn makes no sense whatsoever, but it doesn’t indicate it to be a NoPT entry. This has puzzled a lot of instrument instructors in the area, and the debate raged on for quite some time. Finally a senior controller with Minneapolis Approach was contacted and asked as to what was expected. He said he would not expect a pilot cleared to NAZMY from the east to do a procedure turn, and in fact it could conceivably cause problems if he had other traffic in the area close to the fix. The situation has been resolved, at least locally, by an amendment to the wording of the clearance. Now ATC will state that the pilot is five miles from NAZMY and is cleared straight in for the approach or words to that effect. The 2007 AIM says a procedure turn is “a required maneuver when it is necessary to perform a course reversal.” The bold-face emphasis comes from the 2007 AIM itself. It further states that a procedure turn is not required when an approach can be made directly from a specified intermediate fix to the final approach fix, which somewhat applies to the Maple Lake GPS approach, since NAZMY is both an IAF and an IF. But then the AIM promptly muddies the water by saying in such cases the term “NoPT” is used. Fortunately the TAA GPS approaches have resolved these ambiguities.

One final item should be noted on the topic of procedures turns, and that is the definition of the phrase “procedure turn inbound”. Many instrument students as well as instrument pilots interpret this phrase to mean the point at which you start the turn back towards the final approach course. It is not. Procedure turn inbound is the point at which you turn onto the final approach course.

The bottom line is that unless the procedure turn is a teardrop track or holding pattern in lieu of a procedure turn, today you can pretty much do what you want when it comes to course reversal. Just do it on the protected side and stay within the specified limit.