Aero Nerdery Thread (rotary-curious welcome)

[RobLyman]

I didn't say that. I said there is an unwillingness from many (but not all) of the IPs I'm having to deal with that won't think beyond what their gouge is saying when teaching the training manual.

Also, you were not a straight-stick Army IP. Don't pretend you were....you had the benefit of getting exposure to both services. You've even made comments about how your Navy experience increased/improved your bag of tricks compared to a someone just exposed to the Army training (I still chuckle at your PTP story).

I was wondering if you were still around on the site and if you'd chime in (and welcome it). My intent isn't to degrade your experience, and in fact, it's clear you're understanding the very concept I initially brought up and are willing to discuss it based on actual performance data.

But some large percentage of Check Airmen that I have to fly with clearly don't, and will even refuse to debrief the discussion after the flight. Again, it's not all of them, but it's notable.

LOL. No, REALLY. Army IPs are dipshits. I watched Army IPs time and again teach aero topics, especially compressibility, VRS and retreating blade stall, wrong. You're right, I had the benefit of being in both services with experience as an instructor in both services, something few Army IPs had. Most Army IPs are not college graduates. For me, an NROTC scholarship student, I had to take calculus and physics. I was a math major so I understand the math principles pretty well. If you read books or white papers on the design the Black Hawk, or read books by Proudy for fun, the subtle aspects of helicopter design are fascinating. But for the lowest common denominator of Army IPs, "Lifties" explanations of aerodynamics are difficult to understand, much less teach. What makes them dipshits is that when provided correct explanations of aero topics, they refused to alter their explanation to their students.

Early on at HAATS I flew a flight into a confined area about the size of a football field at 10,000' ish. I was proud I had hit my numbers and flew a great approach and landing. Then I was VERY embarrassed that I had gotten so involved in the landing I hadn't thought about the power required to get back out. I had an abort and a takeoff route picked out, but I had not calculated the OGE power required to get out...only IGE. Getting in with IGE was doable. Getting out? Not as much. This is where the learning occurred. We did several takeoff attempts using IGE power trying to get over the trees without exceeding our artificial power limit and finally made it with only a momentary exceedance of a couple percent Q.

When flying at those altitudes, the aircraft handles differently, so you get better experience than just artificially limiting your power available. I remember one takeoff from a plateau that kicked my ass, and eventually the IP tried it and failed as well, even though he had done it successfully in the past. It involved transitioning to forward flight from a 5' hover down a slight downslope. One third of the way was a 3' drop down before continuing with the fairly smooth downslope. Every time coming off the 3' drop I/we would either mush down and touch the tailwheel or exceed our power available. After about 4-5 attempts we set down and discussed things. We noticed a rock structure just to the left of our path that blocked the 5-10 kt breeze coming from about 30 degrees left of takeoff course. The wind shadow (I'm a sailboat racer as well) from the rock structure occurred as we crossed the 3' drop off. Operating at sea level this probably would not have happened, but the thin air made the aircraft less responsive and allowed that small wind shadow to more negatively affect our aircraft and mush more than it would have at sea level.

I think one reason Vx is not taught a lot is because it is such a gray area in actual aircraft performance. Even IF you can hover OGE, if you are near the limits of your OGE power with respect to ceiling, not ground effect, it is possible you could reach your ability to climb vertically before clearing the obstacle. Slight variations in wind speed, wind direction, turbulence, ground contour, aircraft configuration, etc...could make a difference in Vx. It could be 0 to 15-20 kts. How well do pitot tubes work at that speed?

My technique to fly Vx is to accelerate until you feel the nose try to pitch up. Once you feel the nose pitch up going through translational lift, set your pitch to maintain that AIRSPEED and fly out. Maintaining an airspeed with nothing registering on your pitot tubes takes feel. The 60M with a significant aft CG requires a positive stick forward nose down effort. The 60A/L was fairly neutral. I don't remember what the 60B with a PBA did going through translational lift. AFCS software and stabilator programming could also make differences in Vx, all within an S70 model aircraft. Given that the Navy, Air Force and Coast Guard all followed what the Army did in the beginning, there is no surprise that a) Vx would be different between services, b) Vx would be ambiguous and c) even IPs would not know a lot about it.

 

[JTS11]

LOL. No, REALLY. Army IPs are dipshits. I watched Army IPs time and again teach aero topics, especially compressibility, VRS and retreating blade stall, wrong. You're right, I had the benefit of being in both services with experience as an instructor in both services, something few Army IPs had. Most Army IPs are not college graduates...

Very informative post Rob. I heard nothing but great things about HAATS when I was in. I believe we looked at trying to send some folks, but it didn't work out.

The explicit terms Vx/Vy were never mentioned in our NATOPS, IIRC..but we certainly had charts to show what they were.
Mostly at the FRS, we practiced MGW takeoffs (either running t/o or from a standstill) The maneuvers were based on your 5' HIGE power, and then applying an artificial torque limit based off of that number.

While I was in, our community got a lot better on establishing SOPs regarding power margins for different flight regimes, as a result of some mishaps.

One question. Is modern tech able to calculate all of the power required/power available numbers on the fly for you? Or, is it still scrolling through charts in a pocket checklist?

 

[Random8145]

LOL. No, REALLY. Army IPs are dipshits. I watched Army IPs time and again teach aero topics, especially compressibility, VRS and retreating blade stall, wrong. You're right, I had the benefit of being in both services with experience as an instructor in both services, something few Army IPs had. Most Army IPs are not college graduates. For me, an NROTC scholarship student, I had to take calculus and physics. I was a math major so I understand the math principles pretty well. If you read books or white papers on the design the Black Hawk, or read books by Proudy for fun, the subtle aspects of helicopter design are fascinating. But for the lowest common denominator of Army IPs, "Lifties" explanations of aerodynamics are difficult to understand, much less teach. What makes them dipshits is that when provided correct explanations of aero topics, they refused to alter their explanation to their students.

Early on at HAATS I flew a flight into a confined area about the size of a football field at 10,000' ish. I was proud I had hit my numbers and flew a great approach and landing. Then I was VERY embarrassed that I had gotten so involved in the landing I hadn't thought about the power required to get back out. I had an abort and a takeoff route picked out, but I had not calculated the OGE power required to get out...only IGE. Getting in with IGE was doable. Getting out? Not as much. This is where the learning occurred. We did several takeoff attempts using IGE power trying to get over the trees without exceeding our artificial power limit and finally made it with only a momentary exceedance of a couple percent Q.

When flying at those altitudes, the aircraft handles differently, so you get better experience than just artificially limiting your power available. I remember one takeoff from a plateau that kicked my ass, and eventually the IP tried it and failed as well, even though he had done it successfully in the past. It involved transitioning to forward flight from a 5' hover down a slight downslope. One third of the way was a 3' drop down before continuing with the fairly smooth downslope. Every time coming off the 3' drop I/we would either mush down and touch the tailwheel or exceed our power available. After about 4-5 attempts we set down and discussed things. We noticed a rock structure just to the left of our path that blocked the 5-10 kt breeze coming from about 30 degrees left of takeoff course. The wind shadow (I'm a sailboat racer as well) from the rock structure occurred as we crossed the 3' drop off. Operating at sea level this probably would not have happened, but the thin air made the aircraft less responsive and allowed that small wind shadow to more negatively affect our aircraft and mush more than it would have at sea level.

I think one reason Vx is not taught a lot is because it is such a gray area in actual aircraft performance. Even IF you can hover OGE, if you are near the limits of your OGE power with respect to ceiling, not ground effect, it is possible you could reach your ability to climb vertically before clearing the obstacle. Slight variations in wind speed, wind direction, turbulence, ground contour, aircraft configuration, etc...could make a difference in Vx. It could be 0 to 15-20 kts. How well do pitot tubes work at that speed?

My technique to fly Vx is to accelerate until you feel the nose try to pitch up. Once you feel the nose pitch up going through translational lift, set your pitch to maintain that AIRSPEED and fly out. Maintaining an airspeed with nothing registering on your pitot tubes takes feel. The 60M with a significant aft CG requires a positive stick forward nose down effort. The 60A/L was fairly neutral. I don't remember what the 60B with a PBA did going through translational lift. AFCS software and stabilator programming could also make differences in Vx, all within an S70 model aircraft. Given that the Navy, Air Force and Coast Guard all followed what the Army did in the beginning, there is no surprise that a) Vx would be different between services, b) Vx would be ambiguous and c) even IPs would not know a lot about it.

I see you like to Hawk your experience, that was one heli of a post.

 

[RobLyman]

Very informative post Rob. I heard nothing but great things about HAATS when I was in. I believe we looked at trying to send some folks, but it didn't work out.

The explicit terms Vx/Vy were never mentioned in our NATOPS, IIRC..but we certainly had charts to show what they were.
Mostly at the FRS, we practiced MGW takeoffs (either running t/o or from a standstill) The maneuvers were based on your 5' HIGE power, and then applying an artificial torque limit based off of that number.

While I was in, our community got a lot better on establishing SOPs regarding power margins for different flight regimes, as a result of some mishaps.

One question. Is modern tech able to calculate all of the power required/power available numbers on the fly for you? Or, is it still scrolling through charts in a pocket checklist?

The 60M had on-the-fly calculations for fuel flow, max endurance, Vy, fuel required to waypoints, etc... nut you are still required to go through the performance planning card prior to the flight. In Army flight school this is taught using charts, but in your unit you get to use a computer program. The problem with the inflight automated/technology aspects is that you are still affected by garbage-in garbage-out. You MUST put in the numbers for your intended landing, not where you are currently flying. At HAATS we flew around the location at 500' above the landing site. This allowed us to survey the site and to obtain actual PA for our site (aircraft PA minus 500').

At HAATS, the student in the back of the aircraft went through the charts in the pocket checklist and reported the results to the pilots flying. Of course students swapped out and everyone got the chance to enjoy crunching numbers in the back. My stick buddy actually had difficulty during one flight. Turns out a quick check with a finger pulse-oximeter showed her blood oxygen level had decreased. She was actually getting a little hypoxic. The LZs at HAATS were between 9k and 14k, so you have to be mindful to descend below 10k between LZs to reset your time limits and in some cases, actually boost your blood oxygen levels.

 

[Griz882]

I had the opportunity to talke a few laps around the pattern in an SE-3150 (Alloutte II). The type, and the follow-on modification the Llama, established a number of high altitude records. The one thing that impressed me most was a “pitch limit” meter in the cockpit. It is a basic needle numbered to a red line. If the needle is below maximum available pitch, the pilot knows he has lift or can can can transition to forward flight. There is no in-flight guesswork involved. I have no idea how it works since the helicopter was built in 1960 and was very steam gauge and analog, but it did.

 

[JTS11]

The 60M had on-the-fly calculations for fuel flow, max endurance, Vy, fuel required to waypoints, etc... nut you are still required to go through the performance planning card prior to the flight. In Army flight school this is taught using charts, but in your unit you get to use a computer program. The problem with the inflight automated/technology aspects is that you are still affected by garbage-in garbage-out. You MUST put in the numbers for your intended landing, not where you are currently flying. At HAATS we flew around the location at 500' above the landing site. This allowed us to survey the site and to obtain actual PA for our site (aircraft PA minus 500').

At HAATS, the student in the back of the aircraft went through the charts in the pocket checklist and reported the results to the pilots flying. Of course students swapped out and everyone got the chance to enjoy crunching numbers in the back. My stick buddy actually had difficulty during one flight. Turns out a quick check with a finger pulse-oximeter showed her blood oxygen level had decreased. She was actually getting a little hypoxic. The LZs at HAATS were between 9k and 14k, so you have to be mindful to descend below 10k between LZs to reset your time limits and in some cases, actually boost your blood oxygen levels.

I can't remember, but were there slots at HAATS for non-army crews? Like I said before, I believe we took a look at sending some folks, but it kind of died on the vine. Did HAATS have a pure resident ground syllabus without actual flighttime?

 

[Gatordev]

Great stuff, Rob. I always appreciate your perspective on stuff like this. I worry that it may seem like I (or others) may be trying to argue your points about "Army" stuff because of the limitations of the typed word, when in reality it's just meant as a means for discussion (and learning).

What makes them dipshits is that when provided correct explanations of aero topics, they refused to alter their explanation to their students.

This really seems to be where the underlying issue is. I get the impression that the IP schoolhouse is such a caustic place that graduating from it breeds a superiority complex by many IPs, and that carries over to the civilian side when they get out, even more so when they become management.

Early on at HAATS...

I really wish I could have made it to Canadian Mountain Flying School during my DH tour for the reasons you're talking about. Learning how to figure out they why of something not working and then learning how to use what's available to get out of it has to make you a better pilot if you let it.

I think one reason Vx is not taught a lot is because it is such a gray area in actual aircraft performance. Even IF you can hover OGE, if you are near the limits of your OGE power with respect to ceiling, not ground effect, it is possible you could reach your ability to climb vertically before clearing the obstacle. Slight variations in wind speed, wind direction, turbulence, ground contour, aircraft configuration, etc...could make a difference in Vx. It could be 0 to 15-20 kts. How well do pitot tubes work at that speed?

In a lighter -60 (or a Lakota/-145), I can see that, but it is most definitely a thing to understand (and I'd argue teach) in an aircraft with less power operating at close to MGW (or max weight for the conditions) and has a smaller power to weight ratio. For the -135 in the summer, it's not uncommon to not be able to HOGE at max continuous and then end up topping out at some low HOGE altitude at T/O power. Just like the MGW take off in the -60, you have to nudge it forward (or backward if still trying to climb a bit and you have the room) until it finally catches translational.

Out of my own curiosity, I calculated the power to weight ratios of each. I don't know if these numbers have any actual aerodynamic value, but they're still interesting to compare.

-60R @ 21,500# (Air Capable Ship config, -401C) and 3880 SHP* : .18

-135 P2+ @ 6,400# and 1334 SHP: .21

*(Did they take out the actual SHP number in the Romeo NATOPS? I can't find it in my June 2022 version, so I used the Bravo numbers)

Or to put it another way, half the weight, but one only a third of the power.

Given that the Navy, Air Force and Coast Guard all followed what the Army did in the beginning, there is no surprise that a) Vx would be different between services, b) Vx would be ambiguous and c) even IPs would not know a lot about it.

Sure, but lots of numbers are different between the various series of aircraft. But the concept still exists, especially when we move beyond flying -60s in other professions outside of the military. They're IP and Check Airmen beholden to FAA standards, and the FAA certainly expects you to know what Vx and Vy is as a civilian pilot.