Maintaining airspeed on IAPs with updrafts and downdrafts
Posted by Cautious_Garage_3469@reddit | flying | View on Reddit | 17 comments
I’m training in the Southeast, so I’m dealing with a lot of thermals, updrafts, and downdrafts during the summer. It’s making it very difficult to maintain airspeed on IAPs.
For context, I’m flying an analog PA-28 with a GNS 430. So, hand flying every approach.
I’m typically configured prior to the FAF, trimmed for about 90 knots with one notch of flaps. The issue I’m running into is that, while tracking the glideslope, I often can’t maintain my rate of descent using mainly power. I end up needing to make additional pitch adjustments to stay on the glideslope. Sometimes more pitch than power when we’re getting rocked around a lot. This works in the sense that I stay on glideslope all the way down, but it causes my airspeed to fluctuate more than I’d like. Usually within about +/- 10 knots, but sometimes getting close to or slightly exceeding that.
My main concern is the checkride, specifically staying within ACS standards for airspeed. Is this level of fluctuation normal given the conditions, or is there something I should be doing differently to tighten things up? I can’t seem to consistently hold 90 knots as precisely as I’d like
scottyh214@reddit
Slow down. 90 is quite fast for a PA28. Try around 80 and you’ll be better off.
Low_Sky_49@reddit
Pitch + Power = Performance. You need to ditch “pitch for airspeed, power for altitude” thinking.
Unstable air requires corrections to both pitch and power if you wish to maintain a constant airspeed or constant rate of descent.
Flavortown42069@reddit
This 1000%. Pitch for airspeed, power for altitude works great in smooth air and steady wind. Where I fly (south Texas) it’s often not the case. If you want to stay “stable” it’s a constant dance between changing both sometimes
BagOfMoneyNoChange@reddit
When you feel the airplane sinking, add a little bit of power. When you feel a thermal pushing you up, take a little power out. It doesn't need to be much. 200 or 300 rpm.
Cautious_Garage_3469@reddit (OP)
Unfortunately I’ve found power alone a lot of the time is typically not enough to maintain glideslope given the conditions, especially the past week or so
BagOfMoneyNoChange@reddit
Pitch and power always go together unless you're trying to accelerate or decelerate while straight and level.
Don't think of it as "pitch for airspeed" or "power for altitude." Think of it as "I'm getting a little low, add some pitch and power" or "I'm getting a little high, reduce some pitch and power."
Cautious_Garage_3469@reddit (OP)
Thanks for the advice. I wonder if it could potentially be a symptom of unknowingly over controlling? Anyways, I’ll trying viewing from a more wholistic view as opposed to just “pitch for airspeed power for altitude”.
Al-tahoe@reddit
"Pitch for airspeed, power for altitude" generally does not work well when you're in the front end of the power curve (above Vg). It's great for slowflight though.
When you're moving that fast, pitch is better thought of as a tool to allocate the aircraft's energy between airspeed and altitude. Power constantly adds energy to the system while drag constantly removes. Ch 4 of the AFH breaks this down thoroughly.
nickjohnson@reddit
Great way to put it! Shouldn't it be airspeed and vertical speed, though?
Al-tahoe@reddit
Airspeed is kinetic energy and altitude is potential
BagOfMoneyNoChange@reddit
It could be from overcontrolling. I've seen that a lot with instrument students. Probably a good question to bring up to your CFI.
Don't beat yourself up. Flying an ILS in a light and slow airplane in summer thermals takes a lot of work. Perfection is not expected.
But yes, I wholly encourage you to remember that pitch and power are indeed related.
confusedguy1212@reddit
Go up alone or with an instructor on a fully VFR DAY. From your takeoff run onward record a table with the following pitch and power configurations.
Rotation into Vy. Climb after 1000 feet. Cruise. Initial descent. Cruise in the terminal area with first notch of flaps (useful for non precisions where you step down) Final approach descent (what you’re struggling with).
For each of those write down a power setting and a pitch attitude that gives you consistent returns.
Use that from now on and watch how much more bandwidth you have to deal with anything instrument related. When you’re off a bit you make very minor corrections or check if you’ve deviated from the prescribed configuration. It’ll also give you something to shoot for in terms of trim.
PILOT9000@reddit
You need to forget the pitch for airspeed/power for altitude thing. They are not independent of each other here.
Mispelled-This@reddit
DPEs can see whether deviations are due to poor weather vs poor skills. Just announce the corrections, do your best to stay within standards, and go missed if you can’t.
Ok_Witness179@reddit
Well, stop doing that. Pitch for airspeed, power for altitude. When you try to do it the other way around, it takes too long for your speed to respond to power changes. That's why you're near or out of standard Your vertical path will be fine, though- it's not really that sensitive until you're pretty much at ils minimums.
Pipers drop like a brick when you pull the power, getting high should absolutely not be a problem if you're actually pulling enough power in the up drafts.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
I’m training in the Southeast, so I’m dealing with a lot of thermals, updrafts, and downdrafts during the summer. It’s making it very difficult to maintain airspeed on IAPs.
For context, I’m flying an analog PA-28 with a GNS 430. So, hand flying every approach.
I’m typically configured prior to the FAF, trimmed for about 90 knots with one notch of flaps. The issue I’m running into is that, while tracking the glideslope, I often can’t maintain my rate of descent using mainly power. I end up needing to make additional pitch adjustments to stay on the glideslope. Sometimes more pitch than power when we’re getting rocked around a lot. This works in the sense that I stay on glideslope all the way down, but it causes my airspeed to fluctuate more than I’d like. Usually within about +/- 10 knots, but sometimes getting close to or slightly exceeding that.
My main concern is the checkride, specifically staying within ACS standards for airspeed. Is this level of fluctuation normal given the conditions, or is there something I should be doing differently to tighten things up? I can’t seem to consistently hold 90 knots as precisely as I’d like
Please downvote this comment until it collapses.
Questions about this comment? Please see this wiki post before contacting the mods.
I am a bot, and this action was performed automatically. If you have any questions, please contact the mods of this subreddit.
ReadyplayerParzival1@reddit
Sometimes you just have to accept small deviations. Correct for it where you can. Ultimately the dpe will take the weather into consideration.